TO  THE  MEMORY 

Of 
MY  FATHER 

This  Volume  is  Dedicated 


COPYRIGHT,    1920 
O.  F.  HUNZIKER 


CONDENSED  MILK  and  MILK  POWDER 


THIRD    EDITION 

REVISED  AND  ENLARGED 


PREPARED  FOR  THE  USE  OF 

Milk  Condenseries,  Dairy  Students  and 
Pure  Food  Departments 


By 

OTTO  F.  HUNZIKER,  B.  S.  A.,  M.  S.  A. 

Author  of  "The  Butter  Industry" 
Formerly  Professor  of  Dairy  Husbandry,  Purdue  University 

and 

Chief  of  the  Dairy  Department  of  the 

Indiana  Agricultural  Experiment  Station 

LaFayette,  Indiana 

Now  Manager  Manufacturing  Department  and  Director  Research  Laboratory 

Blue  Valley  Creamery  Co. 

Chicago 


PUBLISHED  BY  THE  AUTHOR 
LA  GRANGE,    ILLINOIS 

1920 


PREFACE 


This  book  treats  of  the  various  phases  of  the  condensed  milk 
and  powdered  milk  industry.  It  discusses  every  step  in  the 
process  of  manufacture,  following  the  milk  from  the  farmer's  door 
to  the  finished  product  in  the  pantry  of  the  consumer.  The  processes 
of  condensing  and  desiccating  milk,  skim  milk,  buttermilk  and  whey 
are  given  special  attention  and  the  defects  of  the  product,  their 
causes  and  prevention  are  explained  in  detail. 

The  inception  of  this  publication  is  the  result  of  innumerable 
and  persistent  calls  for  definite  and  reliable  information  on  the  sub- 
ject of  condensed  milk  and  milk  powder,  from  manufacturers  in  this 
country  and  in  foreign  lands ;  from  parties  contemplating  embarking 
in  the  business ;  from  national  and  state  experiment  stations  which 
are  oftentimes  called  upon  to  investigate  condensed  milk  defects ; 
from  dairy  schools  desiring  to  give  instruction  on  the  subject ;  from 
national  and  state  pure  food  departments,  seeking  information  con- 
cerning the  possibilities  and  limitations  of  manufacture,  in  their 
efforts  to  formulate  and  enforce  standards  and  laws ;  and  from  com- 
mercial chemists  in  need  of  reliable  methods  of  analyses  of  these 
special  dairy  products. 

'The  information  contained  in  this  volume  represents  the  au- 
thor's experience,  covering  a  period  of  twelve  years,  in  the  practical 
manufacture  of  condensed  milk,  as  expert  advisor  to  milk  condens- 
ing concerns  in  the  United  States,  Canada  and  Australia,  and  as 
visitor  of  condensed  milk  and  milk  powder  factories  in  this  country 
and  in  Europe. 

It  is  the  author's  hope  that  the  information  contained  .herein 
may  serve  as  a  guide  to  manufacturers,  investigators,  teachers  and 
food  authorities,  alike ;  that  it  may  assist  in  a  better  understanding 
and  wider  dissemination  of  the  principles,  phenomena  and  facts  in- 
volved in  the  processes  of  manufacture;  and  that  it  may  lift  the 
obstructing  veil  of  unnecessary  secrecy  which  has  hovered  over  these 

4921  GO 


industries  since  their  beginning,  curtailing  their  development  and 
depriving  them  of  much  of  the  light  of  advanced  science  to  which 
they  are  justly  entitled  and  which  they  need  for  their  greatest  devel- 
opment for  the  lasting  benefit  of  the  producer,  manufacturer  and 
consumer  alike. 

O.  F.  HUNZIKER. 
Purdue  University,  March,  1914. 

PREFACE  FOR  THIRD  EDITION 

Since  the  issuance  of  the  First  and  Second  Editions  of  this 
treatise  many  changes  have  taken  place  in  the  various  phases  of  the 
Condensed  Milk  Industry.  Old  processes  have  been  modified  and 
improved,  new  processes  have  been  invented,  the  equipment  used 
for  manufacture  has  undergone  changes,  new  tests  have  been  de- 
vised for  the  determination  of  the  composition  of  the  finished  prod- 
ucts and  the  entire  status  of  the  industry  has  yielded  to  an  unex- 
pected, unforeseen  and  important  evolution. 

Of  the  most  outstanding  new  features  in  this  edition  may 
be  mentioned  the  chapters  on  Directions  for  the  Standardization  of 
the  Sterilizing  Process,  Evaporated  Milk  Control,  Use  of  the  Mojon- 
nier  Viscosimeter,  Manufacture  of  Condensed  Buttermilk  and  But- 
termilk Powder,  New  Patents  and  Processes  for  the  Manufacture  of 
Milk  Powders.  Important  additions  have  also  been  made  to  the 
chapters  on  History  of  the  Industry,  Volume  of  Output,  Markets, 
Exports,  Imports,  Cost  of  Manufacture,  Standardization  of  Con- 
densed Milk,  and  Prevention  of  Condensed  Milk  and  Milk  Powder 
Defects. 

In  preparing  this  Edition,  the  author  has  endeavored  to  com- 
pletely revise  the  old  edition,  incorpoarting  in  the  revised  edition  the 
many  changes  which  the  tooth  of  time  has  wrought  and  to  bring  this 
treatise  in  all  its  important  phases  up-to-date. 

O.  F.  HUNZIKKR. 
Chicago,  111.,  September,  1920. 


CONTENTS 


•'Definition 


PART  I 
CONDENSED  MILK 

Chapter  I 


^History  and  Development — Invention  of  process;  development  of  in- 
dustry; annual  output  in  U.  S.,  1899-1920;  annual  output  in  other 
countries;  list  of  condenseries  by  states Pages  17-29 

Chapter  II 
.gssentials  of  SuitpM*1  T-npati^ns  for  Condenseries — Milk  supply;  water 

supply;  transportation  facilities;  sewage  disposal 

Building  and  Equipment — Material  of  construction;  floors,  walls  and 
ceilings;  ventilation ;  drainage;  general  plan  of  factory;  list  of 
equipment;  economic  arrangement  of  machinery;  sanitary  ar- 
rangement of  machinery •  • Pages  29-43 

Chapter  III 

Milk  Supply — Basis  of  buying  milk;  comparative  prices  paid  for  milk  in 
1914  to   1918  in  the  four  large  condensing  territories  in   U.  S.; 
quality;  control  of  quality;  inspection  at  condensery;  acid  tests 
of  milk;  boiling  test;  sediment  test;  fermentation  tests. 
Factory  Sanitation — Effect  on  patrons;  on  wholesomeness  of  product; 
"^on  marketable  properties;  how  to  keep  factory  in  sanitary  condi- 
tion; can  washing;  care  of  milk  in  factory  prior  to  condensing 
Pages   43-58 


PART  II 
MANUFACTURE  OF  SWEETENED  CONDENSED  MILK 

Chapter  IV 

Definition 

Heating — Purpose;  temperature;  manner;  advantages  and  disadvan- 
tages of  different  methods. 

Addition  of  sugar — kinds  of  sugar;  beet  sugar;  quality  and  amount  of 
sugar;  mixing  the  sugar Pages  59-68 

Chapter  V 
Condensing — Description  of  vacuum  pan;  types  of  coils;  arrangement 

of  coils  for  maximum  rapidity  of  evaporation. 
Condensers — Surface   condenser;   barometric   condenser,   wet-vacuum 

spray  condenser;  care  of  condenser;  expansion  tank;  catch-all. 
Vacuum  Pump — Science  and  practice  of  evaporating  in  vacuo. 
Purpose  of  condensing  in  vacuo;  relation  of  pressure  to  boiling  point; 

relation  of  altitude  to  atmospheric  pressure;   relation   of  steam 

pressure  in  jacket  and  coils,  water  in  condenser,  temperature  in 

pan  and  vacuum,  to  rapidity  of  evaporation. 
Starting  the  Pan. 
Operating  the  Pan. 
Prevention  of  accidents Pages  68-96 


Chapter  VI 

Striking  or  Finishing  the  Batch — Definition;  ratio  of  concentration; 
methods;  appearance  to  eye. 

Beaume  hydrometer;  temperature  correction  of  Beaume;  specific  grav- 
ity of  sweetened  condensed  milk  at  different  degrees  Beaume; 
sampling  the  batch;  drawing  off  the  condensed  milk. 

Cooling — Methods;  equipment;  effect  on  product Pages  96-110 

Chapter  VII 

Filling — In  barrels;  in  cans;  filling  machines. 

Sealing — Kinds  of  seals;  soldering  devices;  solder;  soldering  flux;  gas 
supply Pages  110-116 


PART  III 

MANUFACTURE   OF   UNSWEETENED    CONDENSED   MILK 
EVAPORATED  MILK 

.Chapter  VIII 

Definition 

Quality  of  fresh  milk;  standardizing  milk. 

Heating  the  Milk. 

Condensing. 

Striking. 

Beaume  hydrometer;  temperature  correction  of  Beaume;  calculation 
of  specific  gravity  from  Beaume  reading;  standardizing  evaporated 
milk Pages  117-124 

Chapter  IX 

Homogenizing — Purpose;  principle  of  homogenize!*;  Gaulin  homogen- 
izer;  Progress  homogenizer;  Viscolizer;  operation  of  homogenizer 
Pages  124-129 

Chapter  X 

Cooling — Holding  tanks. 
Filling — Filling  machines;  venthole  cans. 
Sealing — Sealing  machines;  can  testers Pages  129-136 

Chapter  XI 

Sterilizing — Purpose;  sterilizers;  loading  the  sterilizer;  uniform  dis- 
tribution of  heat;  cans  with  tell-tale  thermometers;  temperature 
and  time  exposure;  qualifications  of  processer;  rapid  arid  uniform 
cooling;  fractional  sterilization;  standardization  of  properties  that 
influence  behavior  of  evaporated  milk  toward  heat  of  sterilization ; 
Mojonnier  method  of  evaporated  milk  control;  Mojonnier  equip- 
ment; preparation  of  bicarbonate  of  sodium  solution;  preparation 
of  sample  cans  for  sterilizer;  sterilizing  sample  cans;  testing 
sample  cans  for  viscosity;  Mojonnier  viscosimeter;  importance  of 
proper  viscosity;  factors  that  influence  the  viscosity  and  their 
correlation  to  sterilizing  process;  the  correct  viscosity  for  evapo- 
rated milk;  adding  sodium  bicarbonate  to  batch;  adjusting  steril- 
izing process  to  different  sizes  of  cans;  Should  bicarbonate  of 
soda  be  used? 

Shaking — Purpose;  methods;  speed  of  shaker. 

Incubating Pages  136-162 


Chapter  XII 

Plain  Condensed  Bulk  Milk — Definition;  quality  of  fresh  milk;  heat- 
ing; condensing;  superheating;  striking;  ratio  of  concentration; 
cooling  .- Pages  162-166 

Chapter  XIII 

Concentrated  Milk — Definition;  apparatus  needed;  operation  of  Camp- 
bell process;. advantages  and  disadvantages  of  process. Pages  166-168 

Chapter  XIV 
Condensing  Milk  by  Continuous  Process — Buflovak  rapid  circulation 

evaporator;  description;  operation. 
The  Continuous  Concentrator — Description;  operation. 
The  Ruff  Condensing  Evaporator — Description;  operation;  quality  of 

product  from  continuous  machines. Pages  168-176 

Chapter  XV 

Condensed  Buttermilk — Composition  of  buttermilk;  manufacture;  re- 
moval of  whey  by  gravity;  concentration  by  centrifugal  separa- 
tion; evaporation  in  vacuo;  equipment  necessary. 

Operation — Ripening  of  buttermilk;  preheating;  condensing;  concen- 
tration; testing  for  density;  condensing  buttermilk  by  film  pro- 
cess; packing;  storage;  composition  of  condensed  buttermilk;  mar- 
kets; annual  output  in  U.  S. 

Condensed  Whey  or  Primost -. Pages  176-185 


PART  IV 
FROM  FACTORY  TO  CONSUMER 

Chapter  XVI 

*  Packing — Stamping  and  inspecting  of  cans;  labeling;  labeling  ma- 
chines; wrinkles  and  rust  spots  on  labels;  capacity  of  labeling 
machines. 

Packing  in  Cases — Marking  the  cases;  casers;  packing  for  ex- 
port   .Pages  185-191 

Chapter  XVII 

Storage — Purpose;  effect  of  storage  temperature;  advisability  of  stor- 
ing, 
ransportation   •    Pages  191-194 

Chapter  XVIII 

Markets — Consumption  of  condensed  milk  and  fluid  milk;  market 
prices;  exports  and  imports Pages  194-200 

Chapter  XIX 

Chemieal  Composition  and  Standards  of  Condensed  Milk — Sweetened 
condensed  milk;  water,  solids,  fat,  proteids,  milk  sugar,  sucrose, 
ash,  specific  gravity. 

Evaporated  Milk — Water,  solids,  fat,  proteids,  milk  sugar,  ash;  compo- 
sition of  milk  fats  in  evaporated  milk;  soluble  and  insoluble  curd 
in  evaporated  milk. 

Plain  Condensed  Bulk  Milk. 

Condensed  Milk   Standards ."Pages  200-211 


Chapter  XX 

Sanitary  Purity  of  Condensed  Milk. 
Digestibility. 
Vitamine  Properties. 

Water-soluble  Vitamines — Fat-soluble  vitamines;   anti-scorbutic  vita- 
mines;  effect  of  heat  of  process  on  vitamines Pages  211-217 

Chapter  XXI 

Cost   of   Manufacture — General    discussion;    cost    of    sweetened    con- 
densed milk;  cost  of  evaporated  milk Pages  217-222 


PART  V 
CONDENSED  MILK  DEFECTS,  THEIR  CAUSES  AND  PREVENTIONS 

Chapter  XXII 

Classes  of  Defects. 

Defective  Sweetened  Condensed  Milk — Detailed  discussion  of  the  fol- 
lowing defects:  Sandy,  rough  or  gritty,  settled,  thickened  and 
cheese,  lumpy,  white  and  yellow  buttons,  blown  or  fermented, 
rancid,  putrid,  brown,  metallic Pages  222-252 

Chapter  XXIII 

Defective  Evaporated  Milk — Detailed  discussion  of  the  following  de- 
fects: Curdy,  grainy,  separated  or  churned,  blown  or  fermented, 
brown,  gritty,  metallic Pages  252-270 

Chapter  XXIV 

Adulterations  of  Condensed  Milk — Skimming,  addition  of  animal  and 
vegetable  fats;  imitation  condensed  milk;  annual  output  of;  addi- 
tion of  commercial  glucose;  addition  of  bicarbonate  of  soda  and 
other  alkalies,  addition  of  cream  of  tartar,  addition  of  starch 
Pages  270-275 


PART  VI 
MANUFACTURE  OF  MILK  POWDER 

Chapter  XXV 

Definition 

Kinds. 

History  and  Development;  Annual  Production. 

Description  of  Different  Processes — Doug-drying  processes;  Wimmer 
process;  Campbell  process;  Film-drying  processes;  Just  process; 
Hatmaker  process;  Gathmann  process;  Passburg  process;  Eken- 
berg  process;  Covers  process;  Buflovak  process;  Spray-drying 
processes;  Percy  process;  Stauf  process;  McLachlan  process;  Mer- 
rell-Merrell-Gere  process;  Rogers  process;  Gray  processes;  Dick 
process Pages  275-303 


Chapter  XXVI 

Commercial  Manufacture  of  Milk  Powder  by  Spray  Process — Preheat- 
ing; precondensing;  heating  of  air;  spraying  and  desiccating; 
desiccating  chamber;  spray  nozzles;  spray  pumps;  hot  air  intake 
and  discharge;  recovery  of  desiccated  milk;  bolting,  packing 
Pages  203-315 

Chapter  XXVII 

Composition  and  Properties  of  Milk  Powders — Chemical  composition 
of  milk  powders;  factors  affecting  composition;  solu- 
of  manufacture;  markets;  annual  output Pages  315-330 

Chapter  XXVIII 
Dried  Buttermilk — Composition  of  buttermilk  powder;  annual  output; 

manufacture;  markets. 
Dried  Whey. 
Maltejl  Milk — History  of  malted  milk  industry;  manufacture  of  malted 

milk;  keeping  quality;  markets;  annual  output. 
Federal  Standards  for  Milk  Powders  and  Malted  Milk. .  .Pages  330-335 


PART  VII 

STANDARDIZATION,    TESTS    AND    ANALYSES     OF    MILK,   CON- 
DENSED MILK  AND  MILK  POWDER 

Chapter  XXIX 

Standardization — Purpose;  standardizing  fluid  milk;  standardizing  the 
finished  product;  standardizing  the  sucrose  in  sweetened  con- 
densed milk Pages  335-342 

Chapter  XXX 
Chemical   Analyses — Milk;    specific   gravity;    total    solids;    ash;   total 

nitrogen;  albumin  and  casein;  milk-sugar;  butterfat. 
tSweetened  Condensed  Milk — Specific  gravity;  total  solids;  ash;  pro- 

teids;  milk-sugar;  butterfat;  sucrose. 
Evaporated  Milk — Specific  gravity;   total   solids;   solids   tables;   ash; 

proteids;  milk-sugar;  butterfat. 

Milk  Powder — Total  solids;  ash;  proteids;  milk-sugar;  sucrose;  butter- 
fat Pages  342-365 

Chapter  XXXI 

Mojonnier  Test  for  Fat  and  Solids — Equipment;  directions;  determina- 
tion of  per  cent  fat  and  total  solids  in  milk,  skimmilk,  buttermilk, 
sweetened  condensed  milk,  evaporated  milk,  condensed  bulk  milk, 
milk  powder  and  malted  milk Pages  365-374 

Chapter  XXXII 

Bacteriological  Analyses — Sampling;  dilutions  for  numerical  counts; 
plating;  media  for  total  counts,  acidifiers,  liquefiers  and  yeast  and 
molds;  incubation;  making  counts;  qualitative  determinations. 

Legal  Standards  for  Dairy  Products  by  States. Pages  374-379 


ACKNOWLEDGMENTS 

The  author  desires  to  express  his  appreciation  and 
gratitude  to  Borden's  Condensed  Milk  Co.  for  cuts  show- 
ing portrait  of  Gail  Borden  and  interior  and  exterior 
views  of  milk  condensing  factories;  to  the  Alpine  Evapo- 
rated Milk  Co.  for  cut  showing  portrait  of  John  B.  Mey- 
enberg;  to  the  Helvetia  Milk  Condensing  Co.,  and  to  Hor- 
lick's  Malted  Milk  Co.  for  biographic  data  relating  to  the 
early  history  of  the  industry;  to  Mr.  Wm.  T.  Nardin, 
Attorney,  for  extensive  statistics  on  milk  prices;  to  Mo- 
jonnier  Bros.  Co.  for  valuable  data  relating  to  the  manu- 
facture of  evaporated  milk;  to  Mr.  C.  B.  Fenlon,  Vice 
President  of  the  Rico  Milk  Products  Co.,  for  valuable  in- 
formation relating  to  cost  of  manufacture  and  details  of 
operation;  and  to  the  manufacturers  and  dealers  of  ma- 
chinery and  supplies  related  to  the  industry,  for  their 
many  cuts  for  illustration  in  the  text  and  for  their 
generous  contribution  of  advertisements,  whose  kindly 
and  active  co-operation  made  possible  the  issuance  of 
this  publication. 


Complete  Milk  Condensing  Unit 

for 

Dairy  Schools 
and  Experimental  Laboratories 


The  dairy  school  is  the  manufactory  of  dairy 

knowledge,  the  clearing  house  of  dairy 

thought,  and  the  distributory  of  the 

dairy  gosf>el 


PART  I. 
CONDENSED  MILK 

CHAPTER  I. 

^.i  — 

DEFINITION. 

Condensed  milk  is  cow's  fresh  milk  from  which  a  consider- 
able portion  of  the  water  has  been  evaporated  and  to  which 
sucrose  may  or  may  not  have  been  added. 

There  are  chiefly  two  classes  of  condensed  milk,  namely, 
sweetened  and  unsweetened.  Both  reach  the  market  in  hermet- 
ically sealed  tin  cans  intended  for  direct  consumption,  and  in 
bulk,  intended  for  bakers,  confectioners  and  ice  cream  manu- 
facturers. 

A  portion  of  the  condensed  milk  on  the  market-  is  made 
from  the  chief  by-products  of  milk,  skim  milk  and  buttermilk. 
Condensed  skim  milk  supplies  the  same  markets  as  condensed 
whole  milk  sold  in  bulk.  Condensed  buttermilk  furnishes  a 
valuable  hog  and  chicken  feed.  It  has,  also,  been  recommended 
for  medicinal  purposes,  and  of  late  years  it  has  found  extensive 
use  in  bakeries  and  for  the  manufacture  of  diverse  prepared  foods. 


HISTORY  AND  DEVELOPMENT  OF  INDUSTRY. 

Invention  of  Process. — Condensed  milk  is  the  child  of  the 
nineteenth  century.  Its  origin  does  not  date  back  far,  and  its 
innovation  and  rapid  development  stand  in  sharp  contrast  to 
those  of  the  manufacture  of  butter  and  cheese,  industries  to 
which  reference  is  made  in  the  Old  Testament1  and  the  evolution 
of  which  has  been  very  gradual.  Notwithstanding  the  newness 
of  this  product,  its  manufacture  has  assumed  such  proportions 
that  today  it  occupies  a  prominent  place  among  the  leading 
branches  of  dairy  manufactures. 

The  condensed  milk  industry   was  introduced  at  about  the 


1  Book  of  Genesis,  C.  18,  V.  8:  "And  he  took  butter  and  milk  and  the  calf 
he  had  dressed  and  set  it  before  them." 

Book  of  Job,  C.  10,  V.  10.  "Hast  thou  not  poured  me  out  like  milk  and 
curdled  me  like  cheese." 


18 


HISTORY  AND  DEVELOPMENT 


same  time  as  the  factory  system  of  the  butter  and  cheese  indus- 
try; although,  for  many  years  before  the  invention  of  a  suc- 
cessful process  of  condensing  milk,  methods  had  been  sought 
to  preserve  milk. 

The  American,  Gail  Borden,  the  inventor  of-  the  manufac- 
ture of  condensed  milk,  is  said  to  have  experimented  some  ten 
years  before  he  finally  decided  that  a  semi-fluid  state,  produced 


rig-.  2.     Gail  Borden 

by  evaporation  in  vacuo,  was  the  best  form  of  preservation. 
He  first  applied  for  a  patent  in  1853,  but  it  was  not  until  three 
years  later  that  the  Patent  Office  appreciated  the  originality 
and  value  of  his  claim  sufficiently  to  grant  him  a  patent.  In 
August,  1856,  he  was  awarded  a  patent  on  his  process,  both  by 
the  United  States  and  by  England. 

In  his  application  Mr.  Bordon  says  :1 

"I  am  aware  that  sugar,  and  various  extracts,  have  been  and 


1  "A  Brief  Sketch  of  Gail  Borden,"  by  S.  L.  Goodale,  Secretary  Maine  State 
Board  of  Agriculture,  1872. — Courtesy  of  Borden's  Condensed  Milk  Company. 


HISTORY  AND  DEVELOPMENT  19 

are  now  concentrated  in  vacuo  under  a  low  degree  of  heat,  to 
prevent  discoloration  or  burning,  i  do  not  claim  concentrating 
milk  in  a  vacuum  pan  for  such  a  purpose, -my  object  being  to 
exclude  the  air  from  the  beginning  of  the  process  to  the  end, 
to  prevent  incipient  decomposition.  This  is  important  and  I 
claim  the  discovery." 

The  claim,  United  States  Patent  No.  15,553,  August  19. 
1856,  is  in  the  following  words : 

"Producing  concentrated  sweet  milk  by  evaporation  in  vacuo, 
substantially  as  set  forth, — the  same  having  no  sugar  or  other 
foreign  matter  mixed  with  it." 

Since  the  introduction  of  the  process  of  milk  condensing,  in- 
vented and  patented  by  Borden,  numerous  modifications  of  the 
process,  as  well  as  entirely  different  processes,  have  been  in- 
vented in  this  country  and  abroad,  The  most  characteristic 
among  these  are:  condensation  by  refrigeration,  by  centrifugal 
force,  by  boiling  under  atmospheric  pressure,  by  passing  hot  air 
over  or  through  milk,  etc.  Most  of  these  new  processes  have 
not  proved  commercially  satisfactory,  with  the  result  that  the 
principle  of  the  process,  originally  invented  by  Gail  Borden, 
and  which  consists  of  condensing  the  milk  in  vacuo  to  a  semi- 
fluid liquid,  is  still  made  use  of  in  the  manufacture  of  the  great 
bulk  of  condensed  milk  produced,  both  in  this  country  and 
abroad. 

While  the  claim  of  the  patent  granted  Gail  Borden  was 
that  of  "producing  concentrated  sweet  milk  by  evaporation  in 
vacuo  without  the  admixture  of  sugar  or  other  foreign  mat- 
ter," records  show  that  Gail  Borden  manufactured  sweetened 
condensed  milk,  sold  under  the  famous  Eagle  Brand  label  as 
early  as  1856.  The  first  advertisement  by  Borden  of  unsweet- 
ened condensed  milk  was  recorded  in  Leslie's  Weekly,  May 
22,  1858.  It  reads  as  follows: 

"Borden's  Condensed  Milk.  Prepared  in  Litchfield  County, 
Conn.,  is  the  only  milk  ever  concentrated  without  the  admix- 
ture of  sugar  or  some  other  substance  and  remaining  easily 
soluble  in  water.  It  is  simply  Fresh  Country  Milk,  from  which 
the  water  is  nearly  all  evaporated,  and  nothing  added.  The 
Committee  of  the  Academy  of  Medicine  recommend  it  as  'an 


20 


HISTORY  AND  DEVELOPMENT 


article,  that,  for  purity,  durability  and  economy,  is  hitherto  un- 
equalled in  the  annals  of  the  milk  trade.' 

"One  quart,  by  the  addition  of  water,  makes  two  and  a  half 
quarts, — equal  of  cream,  five  quarts  rich  milk  and  seven  quarts 
good  milk. 

"For  sale  at  173  Canal  Street,  or  delivered  at  dwellings  in 
New  York  or  Brooklyn  at  25  cents  per  quart." 

Development   of  Industry. — The  beginning  was   small,  the 
process  crude  and  the  product  imperfect.     Not  until  the  stren- 
uous years  of  the  war  of  Secession   did   the  value  and  useful- 
ness of  condensed  milk  as  a  com- 
modity  become   fully  recognized. 
During  the  Civil  War  there  was 
a  great  demand  for  this  product 
and  from  that  time  on  the  indus- 
try greAv  with  great  rapidit 

The  first  factory  was  operated 
by  Gail  Borden  in  Wolcottville, 
Litchfield  county,  Connecticut,  in 
the  summer  of  1856,  but  disap- 
pointed in  not  obtaining  means. 
The  first  condensed  milk  factory  .  .  e 

in  America,  woicottviiie,  Conn,      nothing  was  accomplished.  A  sec- 
ond  attempt  was  made  at  Burr- 

ville,  five  miles  distant,  in  1857,  by  a  company  consisting  of  the 
owners  of  the  patent.  A  small  quantity  of  milk  was  here  suc- 
cessfully condensed  and  its  introduction  into  New  York  began. 
Although  admitted  by  all  to  be  superior  to  any  before  made,  it 
was  slow  in  meeting  with  sales  proportional  in  magnitude  to 
the  expenses  incurred.  Yielding  to  the  monetary  revulsion  of 
that  year  the  company  suspended  operations,  leaving  Mr.  Bor- 
den liable  for  bills  drawn,  on  which  he  was  sued. 

It  was  not  until  February,  1858,  when  Mr.  Borden  (with  the 
other  owners  of  the  patent)  associated  himself  with  Jeremiah  Mil- 
bank,  Esq.,  who  advanced  money  to  revive  the  business,  that  he 
could  be  said  to  enjoy  adequate  means  to  develop  his  invention 
and  at  which  time  the  New  York  Condensed  Milk  Company  was 
formed.  Abandoning  Burrville,  the  new  company  established 
work  on  a  more  extensive  scale  in  Wassaic,  Duchess  county, 
New  York,  in  1860.  In  1865,  extensive  works  were  erected  at 


HISTORY  AND  DEVELOPMENT  21 

Elgin,  Illinois.  Borden's  Condensed  Milk  factories  today  num- 
ber upwards  of  fifty,  extending  from  Maine  to  Washington  State 
as  well  as  into  Canada.  The  New  York  Condensed  Milk  Com- 
pany was  incorporated  in  New  Jersey  in  1860  and  in  New  York 
in  1870.  This  company  was  succeeded  by  Borden's  Condensed 
Milk  Company  which  was  incorporated  in  New  Jersey  in  1899. 
In  the  sixties  of  the  last  century,  the  Anglo-Swiss  Con- 
densed Milk  Company  was  organized  in  Switzerland  under  the 
leadership  of  Charles  A.  Page,  then  United  States  Consul  at 
Zurich,  Switzerland,  and  his  brother  George  H.  Page,  and  with 
the  assistance  of  Swiss  and  English  capital.  The  first  factory 
of  that  company  was  built  and  operated  in  1866  at  Cham,  Lake 


Pig-.  4.     Factory  of  Borden's  Condensed  Milk  Co.,  Randolph,  N.  T. 

Zug,  Switzerland,  tinder  the  direction  of  George  H.  Page,  who 
was  its  president  until  1898,  when  he  died. 

This  company  prospered  and  grew  rapidly  in  Europe.  In 
the  eighties  of  the  last  century  it  invaded  the  United  States, 
where  it  built  and  operated  several  large  factories  in  New  York, 
Wisconsin  and  Illinois.  The  American  factories  were  managed 
by  David  Page  and  William  B.  Page,  brothers  of  George  H. 
Page.  In  1902  the  Anglo-Swiss  Condensed  Milk  Company  sold 
its  entire  American  interests,  factories  and  business,  to  Borden's 
Condensed  Milk  Company.  In  1904  the  Anglo-Swiss  Condensed 
Milk  Company  consolidated  with  Henry  Nestle,  of  Vevey,  Lake 
Geneva,  Switzerland,  another  successful  manufacturer  of  con- 
densed milk.  The  company  which  is  now  known  as  the  .Nestle- 
Cham  Condensed  Milk  Company,  is  operating  some  twenty  large 


22 


HISTORY  AND 


condensed  milk  factories  in  European  countries,  with  headquar- 
ters at  Cham,  Switzerland. 

Up  to  the  early  eighties  of  the  last  century,  sweetened  con- 
densed milk  was  the  only  condensed  milk  that  was  put  on  the 
market  and  sold  in  hermetically  sealed  cans,  while  unsweetened 
condensed  milk  was  manufactured  and  sold  open,  largely  direct 
to  the  consumer,  in  a  similar  way  as  market  milk.  The  purity 


PigT.  5.     Pan  Boom  in  Factory  of  Borclen's  Condensed  Milk  Co. 

and  keeping  quality  of  this  unsweetened  condensed  milk,  how- 
ever,  were   greatly   superior  to   market   milk. 

Early  in  1885  the  Helvetia  Milk  Condensing  Company  was 
organized  at  Highland,  Illinois.  This  company  confined  its 
efforts  exclusively  to  the  manufacture  of  evaporated  milk  (un- 
sweetened condensed  milk,  sterilized  by  heat  and  sold  in  her- 
metically sealed  cans).  While,  for  several  years  before  the  or- 
ganization of  this  company,  the  possibilities  of  producing  a 
sterile  unsweetened  condensed  milk  were  essayed  in  laboratory 


HISTORY  AND 


23 


investigations  by  scientists,  and  while  simultaneously  with  the 
commencement  of  operations  of  this  company,  several  other  com- 
panies experimented  on  this  form  of  condensed  milk,  the  Helvetia 
Milk  Condensing  Company  was  the  first  organization  that  suc- 
ceeded in  producing  a  marketable  unsweetened  condensed  milk 
that  was  sterile  and  would  keep  indefinitely. 

The  rudiments  of  the 
process  of  evaporated,  steril- 
ized milk  wrere  introduced  by 
Mr.  John  B.  Meyenberg,  a 
native  of  Switzerland,  who 
formerly  was  operator  in  the 
mother  plant  of  the  Anglo- 
Swiss  Condensed  Milk  Co.  at 
Cham,  Switzerland.  Mr.  Mey- 
enberg, being  a  man  with  an 
inventive  turn  of  mind,  ex- 
perimented on  the  evapora- 
tion and  sterilization  of  milk, 
during  the  years  1880  to  1883. 
As  the  result  of  these  experi- 
ments he  decided  that  it  was 
possible  to  preserve  milk, 
without  the  aid  of  sugar. 
Migrating'  to  this  country,  he 
applied  for,  and  was  granted 
a  patent  on  his  idea  of  pre- 
serving milk  by  sterilization, 
by  the  United  States  Govern- 
ment in  1884  (Patent  No. 
308,422),  and  again  in  1887 
(Patent,  No.  358,213).  Mr. 

Meyenberg  was  also  granted  patent  rights  (Patent  No.  308,421) 
on  apparatus  for  preserving  milk. 

Attracted  to  Highland,  Illinois,  by  reason  of  its  large  Swiss 
population,  on  the  representations  of  Mr.  A.  J.  Pagan,  a  leading 
Highland  citizen,  who  brought  Mr.  Meyenberg  to  Highland  and 
introduced  him  to  the  community,  Mr.  Meyenberg  associated 
himself  with  Mr.  John  Wildi,  then  a  merchant  of  Highland,  who 


Fig*.  6.     John  B.  Meyenberg- 


24  HISTORY  AND  DEVELOPMENT 

at  once  took  a  leading  part  in  the  organization  of  the  Helvetia 
Milk  Condensing  Co.,  early  in  the  year  1885.  Mr.  Meyenberg 
served  as  the  technical  manager  for  the  first  year,  after  which 
he  severed  his  connections  with  his  company  and  became  en- 
gaged in  the  promotion  of  other  evaporated  milk  factories  in 
the  middle  west,  and  on  the  Pacific  Coast.  Mr.  Meyenberg  died 
in  1914. 

During  the  first  year  of  its  existence,  operations  of  the  Hel- 
vetia Milk  Condensing  Company  were  suspended  a  number  of 
times,  both  on  account  of  difficulties  encountered  in  the  technique 
of  successful  manufacture  and  also  for  financial  reasons.  In  an 
endeavor  to  place  the  company  on  a  technically  and  commer- 
cially successful  basis,  the  board  of  directors  took  charge  of  the 
work  with  Mr.  Louis  Latzer  as  technical  manager,  and  the  first 
half  of  the  second  year  was  mostly  devoted  to  experimental 
work.  During  the  third  year,  interruptions  in  the  operations 
were  only  slight  and  after  that  the  company  operated  continu- 
ously and  successfully  until  the  panic  of  1893,  which  marked 
the  last  suspension  of  business  and  which  was  due  to  the  strained 
commercial  conditions  that  prevailed  throughout  the  country. 

The  first  board  of  directors  of  this  company  was  composed 
of  Dr.  Knoebel,  John  Wildi,  George  Roth,  Fred  Kaeser  and 
Louis  Latzer,  with  Dr.  Kno€bel  as  president  and  Mr.  Wildi 
as  secretary  and  treasurer,  and  business  manager.  In  1888  Mr. 
Latzer  became  president,  which  position  he  is  holding  to  the 
present  day.  In-  1907  Mr  Wildi  severed  his  connection  and 
organized  the  John  Wildi  Evaporated  Milk  Co.  with  headquar- 
ters in  Columbus,  Ohio.  Mr.  Wrildi  died  in  1910. 

The  early  development  and  the  vicissitudes  through  which 
this  pioneer  company  in  the  evaporated  milk  business  passed  are 
most  instructively  expressed  by  its  president,  Mr.  Latzer : 

"Very  little  of  the  product  turned  out  the  first  two  years 
would  now  pass  as  standard  goods.  About  the  third  year,  after 
more  knowledge  of  the  physical  and  chemical  properties  of  milk 
and  after  the  introduction  of  the  practice  of  fractional  steriliza- 
tion, had  solved  the  keeping  properties  and  had  improved  the 
physical  condition  of  the  product,  we  felt  that  the  industry  had 
come  to  stay.  After  we  had  gained  more  knowledge  and  expe- 
rience, and  a  lower  standard  of  the  product  was  adopted  by  the 


HISTORY  AND  DEVELOPMENT  25 

industry,,  the  practice  of  fractional  sterilization  was  abandoned 
for  economic  reasons. 

"The  commercial  part  of  the  business  also  had  its  trials  and 
tribulations  in  introducing  a  new  and  comparatively  inferior 
product  of  comparatively  high  cost,  and  to  overcome  the  prej- 
udices of  both  the  trade  and  the  medical  profession. 

"The  problem  thus  confronting  the  company  was  to  im- 
prove the  product,  decrease  its  cost  and  improve  selling  methods 
at  the  least  possible  cost." 

At  first  this  unsweetened  condensed  milk,  of  relatively  thin 
consistency  and  pregnant  with  the  cooked  flavor  resulting  from 
its  exposure  to  high  sterilizing  temperatures,  failed  to  appeal 
to  the  public,  who  had  become  accustomed  to  the  use  of  the 
sweet,  thick  and  semi-fluid  sweetened  condensed  milk.  But  of  late 
years  the  demand  for,  and  the  manufacture  of  this  product, 
evaporated  milk,  has  increased  rapidly,  until  today,  in  this 
country,  its  output  by  far  exceeds  that  of  sweetened  con- 
densed milk. 

Originally  this  unsweetened  sterilized  condensed  milk  was 
labeled  and  sold  under  the  name  of  "Evaporated  Cream."  The 
Federal  Food  and  Drugs  Act  of  1906  caused  the  name  "Evapo- 
rated Cream"  to  be  changed  to  "Evaporated  Milk." 

A  further  important  step  in  the  development  of  the  manu- 
facture of  condensed  milk  occurred  with  the  introduction  of 
the  Continuous  Concentrator,  which  machine  was  developed  by 
the  By-Products  Recovery  Co.,  of  Toledo,  Ohio.  This  company 
was  organized  in  1913  and  their  machine  and  process  are  covered 
by  numerous  United  States  patents.  The  principle  upon  which 
the  Continuous  Concentrator  is  constructed  and  operates  is  as 
follows : 

"To  rapidly  move  a  film  layer  formation  within  a  cylinder 
having  a  heated  surface,  having  means  for  escaping  vapors  and 
means  for  keeping  the  surface  bright  and  clean,  circumferentially 
and  from  the  point  of  inlet  to  the  point  of  outlet." 

Another  type  of  the  film  principle  of  continuous  concentra- 
tion is  represented  in  the  Ruff  Condensing  Evaporator,  manu- 
factured by  the  Cream  Production  Co.,  Port  Huron,  Mich. 

The  Continuous  Concentrator  in  its  present  improved  form 
has  reached  a  state  of  perfection  that  renders  this  machine  appli- 


26 


HISTORY  AND 


cable  for  the  commercial  manufacture  of  the  diverse  forms  of 
condensed  milk  and  milk  by-products. 

The  simplicity  and  economy  of  the  equipment  involved,  the 
simplicity  and  rapidity  of  the  process  and  the  fact  that  no. water 
is  required  for  condensing  the  escaping  vapors,  are  decided  ad- 
vantages over  the  condensation  in  vacuo.  Already  the  demand 
for  these  concentrators  among  condenseries  and  ice  cream  fac- 
tories is  very  great.  This  process  lends  itself  admirably  to  the 
establishment  and  operation  of  small  local  condenseries  and  milk 
shipping  stations  where  milk  is  condensed  and  then  shipped  for 
packing  and  sterilization  to  concentration  plants. 

Annual   Output   of   Condensed   Milk   in   the   United   States 
1899-1919,  Inclusive. 


Years 

Total 
Condensed 
Milk 

Sweetened 
Condensed 
Milk 

Unsweetened 
Condensed 
Milk 

1899— 

Pounds1  .... 

186,921,787 

(5) 

(°) 

Dollars1   

11,888,792 

(5) 

H 

1904— 

Pounds1  .... 

308,485,182 

198,355,189 

110,129,993 

Dollars1   

20,149,282 

13,478,376 

6,670,906 

1909— 

Pounds1   .... 

494,796,544 

214,518,310 

280,278,234 

Dollars1   

33,563,129 

17,345,278 

16,217,851 

1914— 

Pounds2  .... 

883,112,901 

(5) 

(5) 

Dollars3   

58,011,677 

(5) 

(5) 

1917— 

Pounds2  

975,000,000 

(5) 

(5) 

Dollars4   .... 

106,000,000 

(5) 

(5) 

19186— 

Pounds    

1,675,934,234 

507,053,451 

1,168,880,783 

Dollars   

19196— 

Pounds  

1,977,454,805 

674,184,225 

1,303,270,580 

Dollars   

United  States  Census  Report  for  1910. 
United  States  Dairy  Division,  by  Correspondence. 
Value  estimated  at  $3.40  per  case. 
Value  estimated  at  $5.50  per  case. 
Not  reported  separately. 

Potts,    R.    C.,    U.    S.    Bureau    of   Markets,    February    17,    1920,    and    "The 
Market. Reporter,"  U.  S.  Bureau  of  Markets,  Vol.  1,  No.  13,  March .27,  1920. 


HISTORY  AND  DEVELOPMENT  27 

In  this  country,  as  well  as  in  Canada,  Europe,  Australia  and 
New  Zealand,  the  condensed  milk  industry  grew  rapidly.  Every 
succeeding  decade  marked  the  organization  of  new  companies 
and  the  erection  o>f  new  factories  until  today,  there  are  milk  con- 
densing factories  in  nearly  every  civilized  country  within  the 
dairy  belt. 

The  above  figures  may  serve  to  emphasize  the  rapid  growth 
which  the  condensed  milk  industry  in  the  United  States  has 
enjoyed  during  the  last  decade.  The  total  output  of  condensed 
milk  in  1919,  both  sweetened  and  unsweetened,  but  not  includ- 
ing "filled''  condensed  milk  such  as  condensed  goods  modified 
with  vegetable  fats,  nor  condensed  buttermilk  and  uncondensed 
sterilized  canned  milk,  was  1,977,454,805  pounds,  at  an  estimated 
value  of  approximately  $200,000,000.  Calculating  the  ratio  of 
concentration  at  2.5  to  1,  this  output  represents  the  utilization 
of  approximately  4,944,000,000  pounds  of  fluid  milk.  In  1917, 
when  the  total  output  of  condensed  milk  was  975,000,000  pounds, 
representing  the  utilization  of  about  2,437,000,000  pounds  of 
fluid  milk,  the  total  production  of  milk  in  the  United  States 
was  estimated  at  about  84,611,350,000  pounds  of  which  2.9  per 
cent  were  manufactured  into  condensed  milk.  Reliable  figures 
are  not  as  yet  available  of  the  total  production  of  milk  in  trie 
United  States  for  the  year  1919.  Tt  is  estimated  however,  to  be 
about  90,000,000,000  pounds.  On  the  basis  of  the  above  esti- 
mate, about  5.4  per  cent  of  the  total  milk  produced  in  the 
United  States  during  the  year  1919  was  manufactured  in  to  con- 
densed milk. 

A  new  and  unprecedented  impetus  was  given  the  condensed 
milk  industry  in  America  by  the  advent  of  the  World  War.  The 
concentration  of  the  product,  its  wholesomeness  and  high  food 
value,  the  serviceableness  of  its  package  and  its  great  keeping 
quality  rendered  it  indispensable  as  a  food  for  the  army  and  navy, 
as  well  as  for  the  civilian  population  of  the  warring  nations  in 
its  dire  need  for  food.  In  this  great  crisis  in  which  the  food 
supply  of  the  nations  of  the  earth  was  playing  a  most  important 
role,  condensed  milk  has  proved  its  worth  and  the  demand  for 
this  commodity  has  increased  to  tremendous  proportions.  This 
demand  has  been  readily  responded  to  by  the  industry  on  the 
American  continent  and  has  resulted  in  a  vast  increase  of  the 


28  HISTORY  AND  DEVELOPMENT* 

output  of  condensed  milk  and  in  the  erection  of  many  new  and 
large  factories  within  the  short  span  of  the  war. 

The  tremendous  increase  in  the  volume  of  condensed  milk 
manufactured  in  this  country  in  1919  is  due  in  part  also  to  the 
rapidly  growing  consumption  of  ice  cream  and  soft  beverages 
of  which  ice  cream  is  a  constituent,  as  the  result  of  national 
prohibition.  Conservative  estimates  place  the  increase  of  con- 
densed bulk  milk  supplied  to  ice  cream  factories  at  15  to  20  per 
cent  over  previous  years. 

In  1899,  there  were  in  operation  in  this  country  about  fifty 
factories  manufacturing  condensed  milk,  distributed  over  four- 
teen different  states,  New  York  and  Illinois  leading  the  list  by 
over  50  per  cent.  In  1904,  the  Government  estimated  the  total 
number  of  condenseries  in  operation  at  eighty-seven.  In  1914, 
there  were  in  the  United  States  over  two  hundred  milk  condens- 
ing factories,  distributed  over  twenty-three  different  states.  And 
in  1918  Government  statistics  place  the  total  number  of  con- 
denseries at  322,  distributed  over  30  different  states  as  shown 
on  the  following  table  : 

Distribution   of   Milk   Condensing   Factories   in   United   States1 

in  1920. 

Number  of  Number  of 

States                                   Factories  States                                  Factories 

Alabama   1          Missouri    3 

Arizona    3         Nebraska    2 

California 8          New  Hampshire 1 

Colorado    5          New  Jersey  5 

Florida    1          New    York    68 

Idaho   2          North  Dakota   1 

Illinois    31          Ohio    30 

Indiana 11          Oregon   .  .  . 5 

Iowa    2          Pennsylvania    37 

Kansas    5          Rhode  Island  1    ' 

Maine    1          Utah    3 

Maryland   3          Vermont    5 

Massachusetts    2         Virginia    1 

Michigan    24          Washington    19 

Minnesota    2          Wisconsin    40 

Total  30 ^322 

1  Potts,  R.  C.,  U.   S.  Bureau  of  Markets,  1920. 


ESSENTIALS  OF  SUITABLE  LOCATIONS 


29 


Other  countries  in  which  the  condensed  milk  industry  has 
made  rapid  progress  are :  Canada,  Australia,  New  Zealand, 
Switzerland,  Germany,  England,  Ireland.  Holland.  Sweden,  Nor- 
way, Austria,  Japan  and  India.  The  annual  output  of  some  of 
these  countries  is  reported  below. 

Annual  Output  of  Condensed  Milk  in  Different  Countries.1 


Country 

Year 

Pounds 
Condensed  Milk 

Australia              .    .  . 

1916 

45,694,897 

Canada 

1918 

79,807,971 

France 

1902 

4,691,646 

Taoan   . 

1911 

1,200,054 

New  Zealand 

1918 

6,205,400 

Norway  

1914 

33,000,000 

Switzerland    

(1914 

121,253,000 

United   States    . 

(1918  (est.) 
1919 

55,115,000 
1,977,454,805 

CHAPTER    II. 

ESSENTIALS  OF  SUITABLE  LOCATIONS  FOR  MILK 
CONDENSING    FACTORIES. 

Unlike  the  establishment  of  creameries  and  cheese  fac- 
tories, the  building  of  condenseries  and  the  installing  of  the 
necessary  machinery  involve  the  investment  of  large  capital. 
There  is  need  of  a  substantial  building;  and  of  expensive  machin- 
ery. The  supplies  are  numerous  and  must  be  purchased  in  larger 
quantities  before  the  returns  from  the  sale  of  the  manufactured 
product  are  available.  It  is  estimated  that  it  takes  from  three 
to  six  months  before  the  condensed  milk  reaches  the  consumer. 
This  holds  true  especially  in  the  case  of  canned  goods.  The 
fixed  expenses  also  are  comparatively  heavy,  and  do  not  mate- 
rially change  with  a  decrease  or  increase  in  the  milk  supply. 

All  of  these  facts  emphasize  the  importance  of  locating  the 
factory  in  a  territory  most  suitable  for  economic  manufacture. 


1  Pirtle,   T.   R.,   Statistician,   U.   S.  Dairy  Division,  February  12,   1920. 


30  ESSENTIALS  OF  SUITABLE  LOCATIONS 

to  guard  against  heavy  loss  which  would  naturally  result  in  local- 
ities unfavorable  to  the  industry. 

The  chief  factors  to  be  considered  in  this  connection  are : 

Milk  supply 
Water  supply 
Transportation  facilities. 
Other  conditions. 

Milk  Supply. — A  large  supply  of  milk  with  possibilities  for 
extending  the  milk  supply  territory  is  the  first  essential.  The 
condensery  must  have  milk  to  do  business.  The  locality  in  which 
it  is  located  rmrst  be  adapted  for  the  production  of  large  quanti- 
ties of  milk;  it  must  be  a  dairy  country  where  reasonably  large 
herds  are  kept.  Other  things  being  equal,  the  larger  the  milk 
supply,  the  lower  the  cost  of  manufacture.  Where  the  milk 
supply  drops  below  fifteen  thousand  pounds  of  milk  daily,  pro- 
fitable manufacture  becomes  difficult.  Territories  of  gathered 
cream  creameries  are  usually  not  very  desirable.  The  farmers 
generally  have  small  herds  and  are  not  inclined  to  haul  their 
milk  daily.  They  prefer  to  take  their  cream  to  the  creamery 
once  or  twice  per  week,  or  whenever  it  is  convenient  for  them  to 
do  so.  Again,  they  appreciate  the  feeding  value  of  the  skim 
milk  and  depend  on  the  skim  milk  to  raise  their  young- 
stock  and  pigs.  When  they  take  their  milk  to  the  condensery, 
there  is  no  skim  milk  nor  buttermilk  left  for  feeding  purposes. 

The  presence  of  whole  milk  creameries  and  cheese  factories 
renders  a  locality  most  attractive  for  the  establishment  of  milk 
condenseries.  The  farmers  usually  have  reasonably  large  herds, 
they  are  accustomed  to  take  reasonable  care  of  their  milk  and 
to  haul  it  to  the  factory  daily,  and  the  condensery  prices  are 
generally  high  enough  above  the  creamery  or  cheese  factory 
prices  to  induce  the  farmers  to  patronize  the  condensing  factory. 

Territories  in  close  proximity  of  large  consuming  centers, 
though  dairying  may  have  reached  a  high  state  of  development, 
are  not  desirable,  owing  tcs  the  continuous  and  growing  demand 
for  fresh  milk.  Competition  of  this  kind  means  high  prices, 
which  no  business  tactics  are  capable  of  modifying. 

Water  Supply. — The  value  to  the  milk  condensing  plant  of 
a  generous  and  never-failing  supply  of  clean,  cool  water  cannot 


ESSENTIALS  OF  SUITABLE  LOCATIONS  31 

be  overestimated.  The  folly  of  erecting  condenseries  without 
first  ascertaining  the  water  supply  has  in  some  instances  com- 
pelled milk  condensing  companies  to  abandon  new  plants,  merely 
because  of  lack  of  water. 

In  addition  to  the  water  used  in  the  boilers  and  for  wash- 
ing purposes,  large  amounts  of  water  are  necessary  for  condens- 
ing and  for  cooling  the  condensed  milk.  It  is  estimated  that  the 
condensation  of  one  pound  of  fresh  milk  requires  about  three 
gallons  of  water  at  ordinary  temperature,  although  this  amount 
of  water  may  be  considerably  reduced  by  the  use  of  condenser? 
of  maximum  efficiency. 

The  water  must  be  pure.  In  spite  of  all  precautions,  it  will 
come  in  contact,  more  or  less,  with  the  milk.  Though  all  appara- 
tus and  utensils  holding  and  conveying  milk  and  condensed  milk 
may  be  thoroughly  steamed  after  rinsing  with  water,  there  are 
untold  channels  through  which  the  milk  may  beoome  contami- 
nated with  polluted  water.  Frequently,  while  the  milk  is  con- 
densing, the  vacuum  pump  accidentally  stops.  If  the  processor 
fails  to  immediately  shut  o>ff  the  water  supplying  the  condenser, 
water  will  pour  back  from  the  condenser  into  the  milk  in  the 
vacuum  pan.  In  the  case  of  filthy,  polluted  water,  the  entire 
batch  may  be  ruined.  Again,  the  pan  is  usually  rinsed  between 
batches  and,  if  the  water  used  is  unclean,  it  w^ill  contaminate  the 
milk  of  the  succeeding  bath.  Finally,  when  the  heavy  40-quart 
cans  filled  with  condensed  milk  are  set  into  the  cooling  tank, 
water  frequently  splashes  over  into  the  cans.  Here  again  the 
quality  of  the  condensed  milk  in  jeopardized,  unless  the  water 
used  is  pure. 

The  water  must  be  cold.  The  colder  the  water  the  more 
satisfactory  is  the  operation  of  the  vacuum  pan  and  the  smaller 
the  volume  of  water  required  to  condense  a  given  volume  of 
milk.  If  the  temperature  of  the  water  used  in  the  condenser 
rises  much  above  65  degrees  F.,  the  process  of  condensing  may 
become  difficult,  according  to  the  type  of  pan  and  condenser  used. 
Cold  water  is  essential,  also,  for  the  prompt  and  proper  cooling 
of  the  condensed  milk. 

Transportation  Facilities. — It  is  essential  that  the  factory 
have  access  to  one  or  more  railway  lines. 

While,  for  reasons  discussed  under  "Milk  Supply."  it  is  not 


32  ESSENTIALS  OF  SUITABLE  LOCATIONS 

advisable  to  erect  a  factory  in  too  close  proximity  to  large  con- 
suming or  railway  centers,  it  is  equally  undesirable  to  choose 
a  condensery  site  where  transportation  facilities  are  poor. 

Where  access  to  one  railroad  only  can  be  had,  the  factory 
is  at  the  mercy  of  that  road.  Experience  has  shown  that  monop- 
oly of  transportation  usually  means  a  low  standard  of  efficiency 
of  service  and  high  freight  rates.1  On  the  other  hand,  competi- 
tion involves  a  struggle  for  the  survival  of  the  fittest,  and  it 
offers  the  public  all  the  inducements  that  business  ingenuity  and 
enterprise  can  produce.  Where  two  or  more  transportation  com- 
panies are  after  the  business  of  the  same  manufacturing  concern, 
they  will  generally  leave  nothing  undone  in  the  wray  of  accom- 
modations and  low  rates  to  please  the  manufacturer.  The  result 
is  that  the  manufacturer  enjoys  the  advantages  of  efficient  serv- 
ice, good  accommodations  and  reasonable  freight  rates.1 

This  is  a  factor  which  the  condensery  cannot  afford  to  over- 
look, as  the  freight  charges  are  a  very  conspicuous  item  in  the 
expense  account  of  the  milk  condensing  business.  A  part  of  the 
fresh  milk  may  have  to  be  shipped  to  the  factory  by  rail,  all  the 
finished  product  must  leave  the  factory  by  rail  and  the  condens- 
ery is  dependent  on  the  railway  for  its  raw  materials  and  sup- 
plies, such  as  sugar,  tinplate,  solder,  box  shooks,  barrels,  labels, 
oil,  rosin,  gasoline,  coal,  etc.  Prompt  and  efficient  transportation 
is  essential.  Undue  delays  may  cause  the  condensery  serious 
inconvenience  and  loss,  and  may  result  in  the  cancelling  of  im- 
portant orders. 

Other  Conditions. — The  removal  of  the  sewage  of  the  fac- 
tory is  important.  It  may  be  possible  fo.r  the  factory  to  connect 
with  the  town  or  city  sewer,  in  which  case  the  problem  is  easily 
solved.  Where  this  is  not  possible,  a  site  along  a  creek,  river, 
pond  or  lake  may  offer  effective  means  to  take  care  of  the  con- 
densery sewage.  Where  no  such  natural  depository  is  available, 
the  elevation  of  the  site  should  be  sufficient  to  carry  off  the  sew- 
age far  enough  from  the  factory  to  insure  the  plant  against  foul 
odors  and  unsanitary  conditions.  In  the  absence  of  all  of  these 
avenues  for  the  disposal  of  the  sewage,  a  properly  laid-out  sys- 


1  The  matter  of  freight  rates  is  now  largely  regulated  by  the  Federal  De- 
partment of  Transportation. 


BUILDING  AND  EQUIPMENT  33 

tern   of   septic   tanks   with    efficient   filter   beds   may   serve   the 
purpose. 

Where  possible,  it  is  advisable  to  take  advantage  of  hillsides, 
affording  natural  means  to  arrange  and  operate  the  factory  on 
the  gravity  plan. 

BUILDING    AND    EQUIPMENT. 

Material  of  Construction. — Since  the  establishment  of  a  milk 
condensing  factory  involves  the  investment  of  considerable  capi- 
tal, those  willing  to  invest  must  have  faith  in  the  permanency 
of  the  business.  For  a  permanent  business,  a  building  substan- 
tially constructed  is  the  most  economical.  Most  of  the  factories 
belonging  to  the  most  reputable  concerns  are  built  very  sub- 
stantially. However,  there  are  in  this  country  condensing  fac- 
tories in  the  construction  of  which  cheapness  was  the  govern- 
ing factor. 

It  is  beyond  the  realm  of  this  volume  to  furnish  detailed 
specifications  and  plans  for  the  construction  of  condensed  milk 
factories.  Such  information  would  be  of  comparatively  little 
value,  as  such  details  must  of  necessity  vary  with  locality,  ca- 
pacity of  prospective  plant,  type  of  equipment,  system  of  opera- 
tion and  preferences  of  individual  owners.  Such  details  are  best 
decided  on  and  worked  out  for  each  individual  factory  separately 
and  when  needed.  There  are  a  few  fundamental  principles,  how- 
ever, which  apply  to  all  factories  and  to  which  attention  may  be 
briefly  called  here. 

Floors,  Walls  and  Ceilings. — Stone,  brick,  concrete,  concrete- 
steel,  according  to  availability,  are  satisfactory  materials  of  which 
to  construct  a  condensery.  Intersecting  walls  or  partitions  are 
best  constructed  of  similar  material.  If  constructed  of  wood, 
they  should  rest  on  concrete,  brick  or  stone,  built  up  at  least 
two  feet  from  the  floor,  or  the  lower  two  feet  of  which  parti- 
tions should  be  wainscoated  with  an  approved  quality  of  cement 
plaster. 

All  floors  of  the  main  building  should  be  of  cement,  great 
care  being  taken  that  the  foundation  of  these  floors  be  of  uni- 
formly hard  material,  thoroughly  tamped  and  avoiding  soft  spots. 
The  concrete  bed  should  be  at  least  four  inches  in  depth,  con- 
sisting of  one  part  of  cement,  two  parts  of  sand  and  four  parts 


34  BUILDING  AND  EQUIPMENT 

of  gravel.  The  sand  should  be  sharp  building  sand  and  the  gravel 
should  be  washed  pebbles,  ranging1  in  size  from  one-half  to  one 
inch.  The  top  dressing  should  be  not  less  than  one  inch  thick, 
consisting  of  one  part  of  cement  and  one  and  one-half  parts  of 
sharp  building  sand.  It  should  be  carried  up  on  the  walls  and 
partitions  at  least  two  inches,  forming  a  sanitary  cove.  After 
finishing,  the  floors  should  be  allowed  to  harden  for  at  least 
two  weeks.  .This  will  greatly  prolong  their  life.  It  is  advisable 
to  use  cement  hardener  such  as  Master  Builders'  cement,  or 
Lapidolith,  etc.,  which  will  help  to  make  these  floors  more  nearly 
wear-,  water-,  dust-  and  crack-proof.  It  is  difficult  to  keep  the 
condensery  in  sanitary  condition  and  to  protect  the  product 
against  contamination,  unless  the  floors  of  the  factory  are  and 
stay  free  from  cracks  and  holes. 

Ventilation. — A.  proper  and  effective  system  of  ventilation 
is  another  very  important  and  too  often  entirely  neglected  factor 
in  the  planning  of  the  condensed  milk  factory.  This  applies  to 
all  parts  of  the  plant  where  work  is  being  done,  but  it  is  espe- 
cially essential  in  rooms  where  free  steam  escapes.  The  ventilat- 
ing system  should  be  adequate  to  afford  ready  and  quick  escape 
of  steam,  to-  remove  foul  air  and  to  facilitate  the  regulation  of 
temperature.  Unless  free  steam  does  promptly  find  an  exit  from 
the  factory  rooms,  it  condenses  on  the  walls  and  ceilings,  mak- 
ing them  sweat  profusely,  causing  corrosion  of  the  walls  and 
ceiling,  deterioration  of  motors  and  other  similar  equipment, 
and  molding  of  supplies ;  this  is  especially  the  case  during  the 
winter  months.  The  removal  of  foul  air  and  the  control  of  the 
temperature  of  the  air  are  essential  for  the  comfort,  health  and 
efficiency  of  the  employes. 

The  system  of  ventilation  that  will  accomplish  efficient  ven- 
tilation will  of  necessity  vary  with  the  type  of  plant  and  arrange- 
ment of  equipment.  Gravity  ventilation  is,  under  average  con- 
ditions, inadequate  to  produce  satisfactory  results  in  factories, 
like  milk  co<ndenseries,  where  there  is  bound  to  be  much  escape 
of  free  steam.  The  exchange  of  air  is  not  rapid  enough  to  remove 
the  steam  before  it  condenses  on  the  walls  and  ceilings,  espe- 
cially in  cold  weather.  It  is,  therefore,  advisable  to  provide  for 
some  form  of  forced  ventilation.  Under  certain  conditions  of 
construction  an  air  flue  connecting  with  the  smoke  stack  may 


BUILDING  AND  EQUIPMENT  35 

furnish  all  the  ventilation  needed.1  Under  many  other  condi- 
tions, however,  it  is  necessary  to  hood  that  equipment  from 
which  free  steam  escapes  in  large  volume,  such  as  can  washers, 
and  can  sterilizers,  hot  wells,  etc.,  and  to  draw  the  steam  away 
through  ducts  of  adequate  size  by  one  or  more  motor  fans 
located  in  the  outside  wall  or  ceiling. 

Drainage. — All  floors  of  the  manufacturing  rooms  should 
slope  to  facilitate  rapid  drainage.  A  fall  of  one-eighth  inch 
per  foot  is  usually  sufficient.  Large  water-sealed  floor  drains 
should  be  sufficiently  numerous  and  well  placed  in  all  rooms  to 
rapidly  carry  off  water.  The  surface  of  these  floor  drains  should 
be  about  one-half  inch  below  that  of  the  adjoining  floor,  so  as 
to  catch  the  water  readily.  In  the  larger  rooms  open  drain- 
ditches  in  the  cement  floor,  six  to  eight  inches  wide  and  covered 
with  perforated  iron  plates,  are  preferable  to  bell-traps.  They 
may  be  placed  along  the  walls  or  elsewhere.  They  should  be 
not  more  than  forty  feet  apart  and  have  a  fall  of  one-eighth 
inch  to  the  foot,  with  the  floor  sloping  toward  them.  It  is  gener- 
ally most  convenient  to  have  all  the  drain  pipes  enter  into  one 
large  sewer  pipe  not  less  than  ten  inches  in  diameter,  for  a  con- 
densery  receiving  about  fifty  thousand  pounds  of  milk  daily, 
wliich  should  dispose  of  all  the  factory  sewerage.  It  is  advis- 
able to  place  the  main  sewer  pipe  outside  the  building  and  to 
have  it  terminate  in  a  "clean-out."  This  will  afford  more  ready 
access  in  case  the  sewer  is  stopped  up. 

General  Plan  of  Factory. — Most  of  the  condensing  factories 
are  either  one-  or  two-story  buildings.  In  the  case  of  two-story 
buildings  the  first  floor  is  usually  devoted  to  the  boiler  and 
engine  rooms,  vat  room,  well  room,  filling,  sealing  and  packing 
rooms.  On  the  second  floor  are  installed  the  pan  room,  store 
room  for  sugar  and  box  shocks,  the  tinshop  and  possibly  the 
offices.  A  basement  is  sometimes  provided  and  used  for  the  stor- 
ing of  condensed  milk. 

Fig.  7  illustrates  a  floor  plan  of -a  milk  condensing  factory 
with  a  capacity  of  fifty  thousand  pounds  of  milk  daily.  All 
operating  rooms  are  located  on  one  floor.  The  arrangement  of 
machinery  permits  of  the  handling  of  the  milk  on  the  gravity 

1  In  this  case  there  should  be  an  inner  and  outer  stack  with  an  air  space 
between  which  connects  with  the  air  flue. 


36  BUILDING  AND  EQUIPMENT 

plan  or  with  pumps3  according  to  the  topography  of  the  site 
and  the  elevation  of  the  rooms.  The  receiving  room  floor  and 
the  platform  which  accommodates  the  vacuum  pans,  should  be 
seven  to  eight  feet  above  the  main  floor.  In  order  to  take  care 
of  storage  of  water,  sugar,  tin  cans,  barrels  and  box  shooks, 
there  should  be  a  second  floor  over  the  well  room  and  the  filling, 
sealing  and  sterilizing  room.  The  ceiling  of  these  rooms  should 
be  not  less  than  sixteen  feet  above  the  floor. 

The  rooms  are  so  arranged  as  to  necessitate  the  minimum 
expenditure  of  machinery,  conveyors  and  labor.  All  work  rooms 
open  on  the  railway  switch,  and  the  storage  room  is  accessible 
by  two  elevators.  The  well  room,  where  most  of  the  steam  is 
needed,  is  next  to  the  boiler  room,  so  as  to  minimize  condensa- 
tion in  the  steam  pipes.  If  the  main  steam  pipes  are  properly 
insulated,  this  arrangement  should  furnish  the  vacuum  pans  with 
dry  steam.  The  floor  in  the  boiler  room  should  be  two  feet 
below  the  main  floor,  in  order  to  give  additional  fall  for  the  con- 
densation water  from  jacket  and  coils  of  the  vacuum  pans  to  the 
boiler  feed  tank. 

The  partition  between  the  receiving  room  and  testing  room 
is  equipped  with  a  cabinet,  opening  on  both  sides  so  that  the 
sample  bottles  can  be  placed  on  the  shelves  in  the  receiving 
room  and  taken  off  the  shelves  in  the  test  room. 

From  the  weigh  cans  on  the  receiving  platform  the  milk  runs 
direct  into  the  hot  wells,  which  are  sufficient  in  number  to  con- 
veniently divide  the  milk  into  batches  and  to  heat  the  milk  with 
the  least  possible  delay.  The  capacity  of  the  vacuum  pumps  is 
augmented  by  their  close  proximity  to  the  vacuum  pans  and  the 
hot  wells  and  by  the  fact  that  the  water  supply  tanks  are  over- 
head. The  space  to  be  evacuated  is  confined  very  largely  to  the 
vacuum  pan  only,  the  milk  has  to  be  lifted  by  the  vacuum  pump 
but  a  few  feet  and  the  water  runs  into  the  condenser  by  gravity. 

From  the  well  room  the  condensed  milk  is  transferred  to  the 
tanks  on  the  platform  over  the  filling  machines.  The  evaporated 
milk  is  pumped  from  the  cooling  coils  through  the  wall  and  the 
sweetened  condensed  milk  is  raised  to  the  platform  in  ten-gallon 
cans  on  the  elevator,  or  is  forced  by  a  pressure  pump  into  the 
tanks  feeding  the  filling  machines.  The  sealing  benches  are 
equipped  with  self-heating  soldering  coppers.  In  the  place  of  the 


BUILDING  AND  EQUIPMENT 


37 


I 


38  BUILDING  AND  EQUIPMENT 

soldering  benches  and  hand  coppers,  automatic  sealing  machines 
may  be  installed.  The  sterilizers  and  shakers  are  conveniently 
placed  to  take  care  of  the  sealed  evaporated  milk.  The  tin  cans 
for  the  sealing  room  and  the  box  shocks  for  the  packing  room 
are  brought  down  from  the  storage  room  overhead  on  the  ele- 
vator. The  labeling  and  packing  room,  equipped  with  the  label- 
ing-and  box  nailing  machines,  provides  for  considerable  storage 
of  the  finished  product.  Additional  storage  at  a  moderate  and 
uniform  temperature  might  be  provided  for  by  a  basement  under 
the  packing  room.  A  label  stock  room  furnishes  satisfactory 
storage  for  the  labels. 

In  case  the  factory  manufactures  its  own  tin  cans,  a  tinshop, 
equipped  with  the  necessary  machinery  (see  list  of  machinery 
and  equipment)  should  be  located  in  as  close  and  convenient 
proximity  to  the  filling  and  sealing  room  as  possible.  A  suitable 
place  is  directly  opposite  the  filling  room  with  the  railway  track 
separating  the  latter  from  the  tinshop.  The  tinshop  should  have 
two  outside  doors,  opening  out  on  the  track,  and  its  machinery 
should  be  so  arranged  that  the  tin  plate  can  be  unloaded  from 
the  car  at  one  door,  is  moved  back  through  the  machinery  and 
appears  again  in  the  form  of  finished  cans  at  the  other  door, 
directly  opposite  the  filling  room  and  ready  for  the  reception 
of  the  condensed  milk.  Instead  of  erecting  a  separate  building 
for  the  tinshop,  the  latter  may  also  be  conveniently  installed  in 
the  second  story  directly  over  the  filling  room. 

Where  natural  gas  and  gas  from  municipal  corporations  is 
not  available,  one  or  more  gasoline  gas  generators  should  be 
installed.  These  gas  generators  contain  inflammable  material 
and  should,  therefore,  be  located  at  a  reasonable  distance  from 
the  main  building. 

The  tendency  in  factory  construction  today  is  to  do  away 
with  all  partitions  between  operating  rooms,  having  all  manu- 
facturing and  packing  rooms  in  one  large  space.  In  this  case 
it  is  customary  and  economical  to  place  the  vacuum  pan  and 
condensed  milk  storage  tanks  on  an  elevated  platform  and  in- 
stalling the  hotwells,  coolers,  vacuum  pump,  milk  pumps, 
homogenizer,  filling  and  sealing  machines,  sterilizers,  labeling 
and  packing  machines  on  the  main  floor,  which  also  provides 


BUILDING  AND  EQUIPMENT  39 

the   necessary   space    for   the   stock   of   supplies   and   of   canned 
goods. 

List  of  Equipment. — The  following  is  a  list  of  the  principal 
machinery  and  equipment  needed  in  an  up-to-date  condensery 
with  a  capacity  of  fifty  thousand  pounds  of  milk  daily: 

BOILER    BOOM 

Boilers   with   a  total   capacity   of  400  H.   P. 
1  boiler  feed  tank. 
1  boiler  feed  pump. 
1  boiler  water  heater. 

ENGINE    BOOM1 

1  40  H.  P.  engine. 

2  well  pumps,  150  gallons  per  minute  each. 

1  80  light  dynamo. 

Pipe  and  thread-cutting  tools,  anvil  and  forge. 

RECEIVING    BOOM 

2  1000-pound  weigh  cans,  "low  down"  style. 

2  6-beam  milk  scales,  or  other  weighing  arrange- 
ment. 

1  can-washing  machine  with  steam  and  water  jets 
and  air  blower  for  drying  the  cans. 

1   milk  sample  bottle  rack. 

HEATING    AND    CONDENSING    DEPARTMENT 

6  5000-pound  capacity  jacketed  kettles  with  revolv- 
ing agitators  and  superheating  device. 
1  6-foot  vacflum  pan  "^ 

1  7-foot  vacuum  pan    v  or  continuous  concentrators. 

2  vacuum  pumps 

2  500-gallon   standardizing  vats  on  scales. 
1  6-cylinder  homogenizer. 

1  internal  tube  cooler,  capacity  5000  to  8000  pounds 
per  hour,  for  cooling  evaporated  milk,  or 

1  submerged   coil  cooler,  or 

2  36-can  cooling  vats  with  cans,  cross  bars  and  pad- 

dles complete,  or 


1  In  case  municipally  generated  electricity  is  available,  there  is  no  need 
of  a  Dynamo  and  much  of  the  equipment  may  be  supplied  with  direct  drive 
by  motors.  This  would  obviate  the  installation  of  a  steam  engine. 


40  BUILDING  AND  EQUIPMENT 

2  5000-lbs.  circular  cooling  vats  with  vertical  coils 
for  cooling  sweetened  condensed  milk,  or 

1  submerged  coil  cooler  with  high  pressure  pump 
and  two  5000-gallon  glass  enameled  holding 
tanks  with  agitators,  for  both  evaporated  milk 
and  sweetened  condensed  milk. 

1  wash  tank. 

1  elevator. 

1  2-beam  platform  scale. 

1  truck. 

PILLING,   SEALING  AND    STERILIZING   DEPARTMENT 

4  200-gallon  condensed  and  evaporated  milk  vats.1 

2  filling  machines  for  sweetened  condensed  milk. 
2  filling  machines  for  evaporated  milk. 

4  soldering  benches,  5x20  feet,  with  10  self-heating 
soldering  coppers  each,  or 

1  or  more  sealing  machines  with  can-testing  baths, 

the  number  depending  on  type  and  capacity  of 
machine  used. 
2000  wooden  trays  holding  24  16-ounce  cans  each. 

2  sterilizers,  capacity  75   to   100  cases   each,  com- 

plete with  iron  trays. 

1  double  shaker. 

2  trucks. 

LABELING  AND  PACKING  DEPARTMENT 

2  labeling  machines  with  casers 
2  nailing  machines. 
.  2  trucks. 

TESTING    BOOM 

2  24-bottle  Babcock  testers,  with  one  gross  of  stand- 
ard milk  test  bottles  and  accessories,  complete. 
Equipment  for  chemical  and  bacteriological  analyses 
of  milk,  milk  products  and  sugar. 

OFFICES 

Usual  equipment. 

TOILET    BOOMS 

Usual  equipment. 

1  Not  needed  if  well  room  Is  equipped  with  large  holding  tanks. 


BUILDING  AND  EQUIPMENT  41 

OVERHEAD  STORAGE  ROOM 

*  1  50,000-gallon  water  tank.   This  tank  is  preferably 

located  outside  of  factory. 
1  4-beam  platform  scale  for  sugar. 

ADDITIONAL     EQUIPMENT 

1  gasoline  gas  generator  (complete),  needed  in  ab- 
sence of  access  to  natural  gas  or  municipal  gas. 

1  15-ton  ammonia  compressor,  with  ammonia  and 

brine   pipe    lines,   circulating  pump   and   brine 
tank. 

*  TIN    SHOP 

Needed  in  case  cans  are  manufactured  at  the  factory. 

2  squaring  shears. 

2  body  cutting  machines. 

2  lock  seamers. 

6  presses. 

2  crimping  machines. 

2  soldering  floats. 

1  can  tester  with  vacuum  pump. 

1  can  wiper. 

1  lathe  with  tools. 

1  gasoline  gas  generator,  complete. 

1  25  H.  P.  engine  or  motor. 

200  can  crates. 

Economic  Arrangement  of  Machinery. — In  the  arrangement 
and  connection  of  the  machinery,  economy  of  manufacture  and 
sanitation  of  the  product  should  receive  serious  consideration. 
The  machinery  should  be  so  arranged  as  to  reduce  to  the  mini- 
mum the  space,  pumps,  pipes  and  conveyors  needed.  Pumps, 
conveyors,  pipes  and  fittings  are  expensive,  and  the  space  saved 
by  judicious  arrangement  of  the  stationary  machinery  may  be 
used  to  advantage  for  other  purposes. 

Human  muscle  is  the  most  expensive  form  of  motive  power. 
Wherever  muscle  can  be  replaced  by  machinery  and  where,  by 
intelligent  arrangement  of  the  machinery,  unnecessary  steps  and 
handling  can  be  avoided,  the  cost  of  manufacture  is  reduced. 

The  matter  of  insulation  of  ammonia,  brine,  steam  and  water 
pipes  is  an  important  item  as  related  to  the  economy  of  fuel. 


42  BUILDING  AND  EQUIPMENT 

For  proper  and  economical  insulation  the  following  types  of  pipe 
covering  are  recommended : 

Ammonia  and  Brine  Lines. — 

1st  layer  of  tarred  felt. 

2nd  layer  of  1"  thick  hair  felt. 

3rd  layer  of  tarred  felt. 

4th  layer  of  V  thick  hair  felt. 

5th  layer  of  tarred  felt, 

6th  layer  of  wove-felt  paper. 

7th  layer  of  8-oz.  canvas  jacket,  sewed  on. 

8th  layer  of  sizing  and  one  coat  of  lead  and  oil  paint. 

Each  layer  of  hair  felt  must  be  securely  wound  with  twine. 
Each  layer  of  all  material  should  be  coated  with  hot  asphalt, 
applied  while  hot,  excepting  layers,  6,  7  and  8. 

Special  seals  must  be  made  at  all  flanges  and  fittings,  and 
such  flanges  and  fittings  must  be  insulated  independently.  This 
arrangement  will  prevent  damage  to  adjoining  coverings,  should 
fittings  spring  leaks. 

Before  applying  pitch  or  asphalt,  the  necessary  precautions 
must  be  taken  to  have  the  pipes  thoroughly  cjry  and  the  asphalt 
or  pitch  must  be  hot. 

Steam  Lines. — Air  cell  asbestos  covering,  or  covering  of 
equal  insulating  and  lasting  quality,  one  inch  thick  on  pipes, 
and  fittings,  to  be  built  up  of  asbestos  cement  to  a  correspond- 
ing thickness ;  smoothly  finished  and  neatly  canvassed,  with 
metal  bands  at  18"  intervals.  Before  putting  on  the  metal  bands 
the  covering  should  receive  two  coats  of  asbestos  cold  water 
paint. 

Cold  Water  Lines. — Covering  of  wool  felt,  tar  paper  lined, 
sectional,  one  inch  thick  on  pipes ;  fittings  to  be  built  up  to  a 
corresponding  thickness  with  one  inch  hair  felt,  the  entire  line 
should  be  neatly  finished  with  a  graded  mixture  of  Portland 
cement  and  asbestos  cement,  and  canvas-jacketed  and  equipped 
with  metal  bands  at  18"  intervals.  Before  putting  on  the  metal 
bands,  the  covering  should  receive  two  coats  of  asbestos  cold 
water  paint. 

Sanitary  Arrangement  of  Machinery. — Milk  pumps,  milk 
pipes,  milk  troughs  and  other  milk  conveyors  are,  at  best,  ene- 


SUPPLY  43 

mies  of  sanitation.  They  should  be  avoided  wherever  possible. 
The  gravity  system  of  conveying  milk  should  be  used  in  pref- 
erence to  the  pumping  system.  Milk  pipes  should  be  short  and 
accessible ;  all  vats  sould  be  of  sanitary  construction  ;  wooden 
jackets  should  not  be  tolerated ;  all  seams  in  the  vats  and  ket- 
tles should  be  well  flushed  with  solder;  milk  pumps  should  be 
brass  lined;  all  milk  pipes  should  be  of  black  iron  pipe  made 
smooth  on  the  inside  by  sandblasting,  or  of  galvanized  iron  or 
copper  heavily  tinned  over  on  the  inside:  long  lines  of  milk 
pipes  should  be  equipped  with  unions  at  short  distances ;  crosses 
or  sanitary  couplings  should  be  used  in  place  of  elbows,  in 
order  to  render  all  sections  of  the  milk  pipes  easily  accessible 
to  flue  brushes. 

CHAPTER  III. 
MILK  SUPPLY. 

Basis  of  Buying  Milk. — The  prices  which  the  condensery 
pays  the  patrons  are  not  usually  governed  by  any  board  of  trade. 
They  do-  not  even  necessarily  follow  the  quotations  of  the  but- 
ter and  cheese  market,  though  they  naturally  bear  a  more  or  less 
definite  relation  to  them.  In  normal  times  condensery  prices 
average  from  about  twenty  to  fifty  cents  higher  per  hundred 
pounds  of  milk  than  those  paid  by  creameries  and  cheese  fac- 
tories. 

The  relation  between  condensery  prices  on  the  one  hand 
and  creamery  and  cheese  factory  prices  on  the  other,  varies  prin- 
cipally with  the  market  demand  for  the  finished  product  and, 
the  season  of  the  year. 

The  greater  the  demand  and  the  brisker  the  market  for 
condensed  milk,  the  greater  usually  is  the  difference  in  price 
for  whole  milk.  Thus,  during  the  war  the  export  demand  for 
condensed  milk  was  very  great.  This  resulted  in  an  extreme 
rise  of  prices  which  condenseries  offered  for  milk  over  those 
paid  by  creameries  and  cheese  factories,  at  least  in  so  far  as 
exportation  was  not  too  greatly  limited  by  shortage  in  shipping 
facilities. 

It  is  customary  for  the  condenseries  to  pay  the  highest  dif- 
ferential over  and  above  creamery  and  cheese  factory  prices  in 


44  MILK  SUPPLY 

winter,  during  the  time  of  low  supply,  and  to  drop  prices  very 
close  to  those  of  creameries  and  cheese  factories  in  summer, 
during  the  flush  of  the  milk  producing  season.  Nardin1,  assem- 
bled comparative  milk  prices  paid  by  condenseries  and  cream- 
eries and  cheese  factories  in  the  four  main  condensed  milk-pro- 
ducing sections  of  this  country,  Illinois,  Newr  York  and  Penn- 
sylvania, Wisconsin,  and  the  Pacific  Coast  States,  for  the  years 
1914  to  1918  inclusive.  These  prices  have  been  summarized  in 
the  following  table.  They  show  that  in  some  instances  condensery 
prices  exceeded  creamery  and  cheese  factory  prices  by  over  one 
dollar,  while  there  were  times  in  summer  when  condensery  prices 
even  dropped  slightly  below  creamery  and  cheese  factory  prices. 
Formerly  condensery  prices  were  announced  by  the  respect- 
ive concerns  from  three  to  six  months  in  advance.  Of  late 
years  this  practice  has  been  more  and  more  abandoned  and  quo- 
tations are  issued  in  advance  for  one  month  only.  The  Midwest 
Milk  Manufacturers,  representing  the  milk  dealers,  market  milk 
plants  and  condenseries  in  the  Chicago  milk  district  and  the 
middle  western  states,  confer  on  the  price  to  be  paid  for  milk 
for  the  succeeding  month,  toward  the  close  of  the  preceding 
month,  and  announce  these  prices  for  the  coming  month. 

Generally  speaking,  and  as  Nardin  points  out,  ''the  price 
in  Illinois  is  subject  to  prices  of  fresh  milk  distributed  in  Chi- 
cago and  St.  Louis.  Prices  in  New  York  and  Pennsylvania 
have  been  subject  to  the  influences  of  the  New  York  Dairymen's 
League,  and  the  price  of  fresh  milk  for  distribution  in  the  City 
of  New  York.  The  Wisconsin  price  is  most  largely  influenced 
by  butter  and  cheese  prices.  The  Pacific  Coast  is,  on  account 
of  freight  rates,  somewhat  isolated  from  the  rest  of  the  coun- 
try, and  the  production  of  evaporated  milk  on  the  coast  has  been 
larger  in  proper  to  the  demands  for  fresh  milk  for  distribu- 
tion in  coast  territory,  than  perhaps  in  any  other  part  of  the 
country." 

The  milk  condenseries,  as  a  whole,  have  been  slow  in  adopt- 
ing the  butterfat  content  of  milk  as  their  basis  for  payment. 
Even  up  to  a  few  years  ago  most  condenseries  were  paying 
for  the  milk  on  the  one  hundred  weight  basis  and  some  factories 

1  Nardin,  Wm.  T.,  Memorandum  on  Federal  Trade  Investigation  of  Milk 
Manufacturers,  1918. 


MILK  SUPPLY 


45 


Comparison  of  Whole  Milk  Prices  Paid  by  Milk  Condenseries  in 
the  Four  Large  Condensing  Territories  in  the  United  States, 
with  Whole  Milk  Values  Based  on  Market  Prices  of  Butter 

and  Cheese. 


Sections  of  Country 

£ 

| 

1 

n 

1 

= 

1 

by  Years 

3 

1 

1 

! 

a 

| 

* 

§ 

1 

& 

1 

f, 

£ 

^ 

•< 

S 

ijj 

3 

02 

O 

1914 

Illinois: 

Mean  condensery  price  . 

1.96 

1.87 

1.72 

1.52 

1.31 

1.22 

1.45 

1.56 

1.60 

1.77 

1.79 

1.82 

Value  in  butter  &  cheese 

1.34 

1.27 

1.25 

1.17 

1.14 

1.12 

1.10 

1.19 

1.17 

1.15 

1.21 

1.21 

New  York  and 

Pennsylvania: 

Mean  condensery  price  . 

1.96 

1.76 

1.73 

1.41 

1.24 

1.19 

1.35 

1.50 

1.64 

1.89 

2.01 

1.90 

Value  in  butter  &  cheese 

1.34 

1.27 

1.25 

1.17 

1.14 

1.12 

1.10 

1.19 

1.17 

1.15 

1.21 

1.21 

Wisconsin: 

Mean  condensery  price  . 

1.87 

1.82 

1.79 

1.62 

1.40 

1.28 

1.43 

1.47 

1.50 

1.72 

1.77 

1.80 

Value  in  butter  &  cheese 

1.34 

1.27 

1.25 

1.17 

1.14 

1.12 

1.10 

1.19 

1.17 

1.15 

1.21 

1.21 

Pacific  Coast: 

Mean  condensery  price  . 

1  73 

1.69 

1.66 

1.58 

1.42 

1.45 

1.51 

1.65 

1.74 

1.69 

1.71 

1   61 

Value  in  butter  &  cheese 

1.34 

1  ?7 

1.25 

1.17 

1.14 

1.12 

1.10 

1.  19 

1.  17 

1.15 

1  21 

1    21 

1916 

Illinois: 

Mean  condensery  price  . 

1.85 

1.83 

1.72 

1.51 

1.27 

1.20 

1.35 

1.47 

1.50 

1.66 

1.77 

1.81 

Value  in  butter  &  cheese 

1.25 

1.26 

1.19 

1.21 

1.20 

1.15 

1.10 

1.03 

1.07 

1.13 

1.24 

1.40 

New  York  and 

Pennsylvania: 

Mean  condensery  price  . 

1.95 

1.75 

1.72 

1.41 

1.19 

1.15 

1.30 

1.52 

1.61 

1.87 

2.00 

2.05 

Value  in  butter  &  cheese 

1.25 

1   ?6 

1.19 

1.21 

1.20 

1.15 

1.10 

1.03 

1.07 

1.13 

1.24 

1   40 

Wisconsin: 

Mean  condensery  price  . 
Value  in  butter  &  cheese 

1.82 
1.25 

1.82 
1  ?fi 

1.70 
1.  19 

1.45 
1.21 

1.30 
1.20 

1.22 
1.  15 

1.40 
1  10 

1.43 
1.03 

•1.48 
1  07 

1.65 
1  13 

1.74 
1.24 

1.72 
1   40 

Pacific  Coast: 

Mean  condensery  price  . 

1.51 

1.51 

1.35 

1.30 

1.22 

1.29 

1.38 

1.39 

1.41 

1.50 

1.54 

1.59 

Value  in  butter  &  cheese 

1.25 

1.26 

1.19 

1.21 

1.20 

1.15 

1.10 

1.03 

1.07 

1.13 

1.24 

1.40 

1916 

Illinois: 

Mean  condensery  price  . 

1.82 

1.74 

1.63 

1.64 

1.46 

1.34 

1.52 

1.67 

1.67 

1.98 

2.12 

2.25 

Value  in  butter  &  cheese 

1.37 

1.42 

1.46 

1.42 

1.27 

1.21 

1.18 

1.28 

1.47 

1.57 

1.87 

1.86 

New  York  and 

Pennsylvania: 

Mean  condensery  price  . 

1.94 

1.93 

1.74 

1.50 

1.36 

1.27 

1.43 

1.62 

1.80 

2.42 

2.53 

2.57 

Value  in  butter  &  cheese 

1.37 

1.42 

1.46 

1.42 

1.27 

1.21 

1.18 

1.28 

1.47 

1.57 

1.87 

1.86 

Wisconsin: 

Mean  condensery  price  . 

1.78 

1.72 

1.69 

1.67 

1.52 

1.42 

1.50 

1.60 

1.67 

1.95 

2.15 

2.35 

Value  in  butter  &  cheese 

1.37 

1.42 

1.46 

1.42 

1.27 

1.21 

1.18 

1.28 

1.47 

1.57 

1.87 

1.86 

Pacific  Coast: 

Mean  condensery  price  . 

1.65 

1.66 

1.64 

1.53 

1.52 

1.47 

1.52 

1.62 

1.69 

1.80 

1.92 

1.98 

Value  in  butter  &  cheese 

1.37 

1.42 

1.46 

1.42 

1.27 

1.21 

1.18 

1.28 

1.47 

1.57 

1.87 

1.86 

1917 

Illinois: 

. 

Mean  condensery  price  . 

2.25 

2.12 

2.05 

2.37 

2.13 

1.92 

2.20 

2.38 

2.52 

3.00 

3.18 

3.28 

Value  in  butter  &  cheese 

1.76 

1.84 

1.99 

2.04 

2.02 

1.88 

1.93 

2.01 

2.21 

2.19 

2.14 

2.19 

New  York  and 

Pennsylvania: 

Mean  condensery  price  . 

2.49 

2.44 

2.32 

2.24 

2.21 

2.12 

2.39 

2.83 

2.91 

3.00 

3.77 

3.52 

Value  in  butter  &  cheese 

1.76 

1.84 

1.99 

2.04 

2.02 

1.88 

1.93 

2.01 

2.21 

2.19 

2.14 

2.19 

Wisconsin: 

Mean  condensery  price  . 

2.36 

2.25 

2.12 

2.29 

2.21 

1.93 

2.27 

2.45 

2.43 

3.19 

3.32 

3.22 

Value  in  butter  &  cheese 

1.76 

1.84 

1.99 

2.04 

2.02 

1.88 

1.93 

2.01 

2.21 

2.19 

2.14 

2.19 

Pacific  Coast: 

Mean  condensery  price  . 

2.06 

2.01 

2.02 

2.09 

2.14 

2.19 

2.32 

2.27 

2.58 

2.67 

2.67 

2.81 

Value  in  butter  &  cheese 

1.76 

1.84 

1.99 

2.04 

2.02 

1.88 

1.93 

2.01 

2.21 

2.19 

2.14 

2.19 

1918 

Illinois: 

Mean  condensery  price  . 

3.28 

3.15 

2.95 

2.67 

2.10 

1.90 

2.32 

2.80 

2.98 

3.42 

3.74 

3.83 

Value  in  butter  &  cheese 

2.24 

2.40 

2.16 

2.00 

2.01 

2.01 

2.11 

2.19 

2.48 

2.78 

2.77 

3.09 

New  York  and 

Pennsylvania: 

Mean  condensery  price  . 

3.90 

3.68 

3.40 

2.65 

2.61 

2.00 

2.29 

2.85 

3.16 

3.78 

3.96 

4.17 

Value  in  butter  &  chees* 

2.24 

2.40 

2.16 

2.00 

2.01 

2.01 

2.15 

2.19 

2.48 

2.78 

2.77 

3.09 

Wisconsin: 

Mean  condensery  price  . 

3.28 

3.13 

2.88 

2.59 

2.21 

2.07 

2.32 

2.80 

2.98 

3.40 

3.74 

3.84 

Value  in  butter  &  cheese 

2.24 

2.40 

2.16 

2.00 

2.01 

2.01 

2.15 

2.19 

2.48 

2.78 

2.77 

3.09 

Pacific  Coast: 

Mean  condensery  price  . 
Value  in  butter  &  cheese 

2.84 
2.24 

2.81 
2.40 

2.66 
2.16 

2.35 
2.00 

2.27 
2.01 

2.28 
2.01 

2.50 
2.15 

2.81 
2.19 

3.12 
2.48 

3.30 

2.78 

3.41 
2.77 

3.51 
3.09 

46  MILK  SUPPLY 

were  still  clinging  to  the  custom  of  buying  milk  by  the  quart, 
using  the  yardstick  for  remnant  cans.  Other  factories  paid  a 
stated  price  per  hundred  weight  for  all  milk  testing  say  4  per 
cent  fat  and  over  and  made  corresponding  reductions  for  milk 
containing  less  than  4  per  cent  fat.  Still  others  paid  a  premiurn, 
for  milk  testing  above  4  per  cent  fat.  A  few  concerns  only 
bought  milk  on  the  straight  butterfat  basis. 

As  far  as  the  condensery  is  concerned  it  is  entirely  feasible 
to  pay  for  all  milk  strictly  on  the  butterfat  basis.  Milk  rich  in 
fat,  and  therefore  rich  in  solids,  yields  more  condensed  milk  than 
milk  poor  in  fat.  To  pay  by  the  hundred  weight,  regardless  of 
quality  is  a  practice  which  discriminates  in  favor  of  breeds  of 
low-testing  milk  and  against  breeds  of  high-testing  milk.  This 
practice  has,  in  fact,  had  the  result  that  in  the  milk  supply  ter- 
ritory of  these  condenseries  the  breeds  and  individuals  of  cows 
producing  low-testing  milk  were  encouraged  and  developed  until 
they  largely  predominated,  at  the  expense  of  breeds  of  cows  pro- 
ducing high-testing  milk.  This  situation  in  turn  was  responsible 
for  the  popular,  though  erroneous  impression,  that  milk  from  the 
Holstein,  Ayrshire  and  Brown  Swiss  breeds  is  better  suited  for 
milk  condensing  purposes  than  milk  from  the  Channel  Island 
breeds. 

Within  the  last  half  decade,  during  which  the  condensed 
milk  industry  has  experienced  SO'  great  a  development,  the  great 
majority  of  American  condenseries  have  abandoned  their  old 
way  of  paying  for  milk  by  volume,  or  weight  .only.  Many  con- 
densing concerns  are  now  buying  their  milk  on  the  straight  but- 
terfat basis  and  nearly  all  of  the  other  condenseries  pay  for  their 
milk  on  the  basis  of  a  standard  fat  content,  penalizing  the  farmer 
by  lower  prices  for  milk  that  falls  below  a  specified  per  cent 
of  fat,  and  giving  him  a  bonus  for  milk  in  which  the  per  cent 
of  fat  is  over  the  standard  figure  specified.  Thus  for  example 
the  price  quoted  may  apply  to*  100  Ibs.  of  3.5  per  cent  milk  with 
an  added  differential  of  say  4  cents  for  each  one  tenth  per  cent 
fat  above  3.5  per  cent  and  a  deducted  differential  of  4  cents  for 
each  tenth  per  cent  fat  below  3.5  per  cent. 

In  countries  where  one  breed  overwhelmingly  predominates 
or  where  the  predominating  breeds  all  yield  mil,k  of  similar  rich- 
ness and  where  the  freshening  of  the  majority  of  cows  is  fairly 


MII.K  SUPPLY  47 

evenly  distributed  over  the  twelve  months  of  the  year,  the  milk 
generally  continues  to  be  bought  on  the  basis  of  its  Aveight  or 
volume,  and  not  by  test.     Under  these  conditions  the  objection 
of  not  paying  on  the  butterfat  basis  is,  in  part  at  least,  removed. 
The  great  bulk  of  the  milk  supply  reaches  the  condensery 
by  wagon  or  by  motor  truck.    Usually  part  of  the  cost  of  trans- 
portation is  borne  by  the  factory  and 
part  by   the   farmer.    Some   milk  con- 
densing concerns  operate  concentration 
points  to  which  the  milk  is  hauled  by 
the  patrons,  and  from  which  it  is  hauled 
to  the  factory  in  large  glass-lined  tanks 
Pig-,  s.  mounted  on  motor  trucks.    Shipments 

Giass-iinea    steel    tank    on     by  rail  are  less  common  in  this  country, 
truck  for  transporting-         the  uncertainty  of  rail  transportation, 

fluid    milk    to    con-  .          .         r  ,    .  .  ,. 

densery  with    its    frequent    delays,   jeopardizes 

Courtesy  of  The  Pfaudier  Co.     the  quality  of  the  milk.     Payments  for 

the  milk  are  generally  made  monthly. 

Quality. — The  quality  of  the  fresh  milk  is  the  first  and  most 
important  factor  to  be  considered.  The  milk  condensing  factory, 
ignoring  this  fact  and  accepting  milk  from  unsanitary  dairies 
and  careless  dairymen,  is  bound  to  pay  the  penalty  for  such 
neglect  sooner  or  later. 

Polluted  milk  and  milk  that  has  not  been  cooled  promptly 
and  to  a  reasonably  low  temperature  on  the  farm,  may  pass 
through  the  process  successfully,  if  it  is  not  too  sour.  The  con- 
densed milk  made  from  it,  though,  is  inferior  in  flavor  and  keep- 
ing quality,  and  usually  shows  signs  of  deterioration  and  decay 
before  it  reaches  the  consumer.  The  risk  of  handling  such  milk- 
is  very  great;  it  may  result  in  total  loss  to  the  manufacturer. 
The  trouble  may  and  often  does  begin  before  the  process  is  com- 
pleted. Unclean,  abnormal,  or  partly  fermented  milk,  when  sub- 
jected to  the  process,  is  prone  to  curdle  and  whey  off;  the  con- 
densed milk  becomes  lumpy  and  shows  other  defects.  This  is 
especially  true  where  superheating  is  practiced  and  where  evap- 
orated milk  is  made. 

Milk  that  has  received  the  best  of  care  on  the  farm  may  be 
detrimental  to  the  interests  of  the  condensery,  if  it  comes  from 
cows  less  than  thirty  days  before  their  parturition,  or  from  fresh 


48  MILK  SUPPLY 

cows  within  the  first  seven  days  after  calving,  or  from  cows 
otherwise  in  abnormal  condition.  Such  milk  is  often  abnormal 
in  its  chemical  properties,  and,  when  subjected  to  high  tempera- 
tures, undergoes  changes  that  make  its  manufacture  into  a  mar- 
ketable condensed  milk  difficult. 

Control  of  Quality. — Every  well  managed  milk  condensing 
factory  plays  the  part  of  an  educator  in  the  production  of  sani- 
tary milk.  The  condensery  usually  issues  a  set  of  rules,  setting 
forth  specifically  the  conditions  under  which  the  milk  coming 
to  the  factory  shall,  or  shall  not  be  produced.  Copies  of  these 
rules,  which  are  generally  a  part  of  the  contract,  are  placed  in 
the  hands  of  all  patrons.  The  condensery  employs  one  or  more 
dairy  inspectors  whose  business  it  is  to  see  that  the  rules  are 
rigidly  enforced.  These  rules  cover,  in  general,  the  following 
principal  points: 

1.  Cows. — The  milk  must  come  from  healthy  cows.     Milk 
from  cows  that  are  diseased,  or  that  have  a  diseased  udder,  or 
that  are  otherwise  in  poor  physical  condition,  will  be  rejected. 

2.  Feed  and  Water. — Do  not  feed  weeds,  roots,  or  other  feed 
stuffs  possessing  strong  and  obnoxious  odors,  such  as  onions, 
garlic,  turnips,  cabbage,  wet  distillery  slops,  decayed,  musty  or 
sour  silage,  or  other  fermented  feed. 

3.  Lactation  Period. — Reject  all  milk  from  cows  less  than 
thirty  days  before,  and  of  the  first  seven  days  after  calving. 

4.  Milkers  and  Milking. — Milk  with  clean,  dry  hands  into 
clean  utensils  and  remove  the  milk  to  the  milk  room  immediately 
after  drawn. 

5.  Straining. — Strain  the  milk  in  the  milk  room  through  a 
fine  wire  mesh  strainer  (80  to  100  meshes  to  the  inch).    Do  not 
use  cloth  strainers. 

6.  Cooling. — Cool  the  milk  to  60  degrees  F.  or  below  and 
keep  it  at  that  temperature  until  it  reaches  the  factory.    Do  not 
mix  the  warm  morning's  milk  with  the  cold  night's  milk;  cool 
the  morning's  milk  before  mixing,  or  send  it  to  the  factory  in 
separate  cans. 

7.  Care  of  Utensils. — 'Rinse  with   cold   water,  wash  with 
warm  water  and  washing  powder,  and  rinse  with  boiling  water 


MII<K  SUPPLY  49 

all  milk  utensils  thoroughly  after  use ;  keep  them  in  a  clean  place 
between  milkings.  Do  not  store  the  milk  on  the  farm  in  cans 
that  have  not  been  washed  by  the  factory. 

8.  Stables. — Whitewash  the  stable  twice  every  year  and  re- 
move manure  daily.  (Some  condenseries  furnish  spray  pumps 
for  applying  whitewash.) 

Inspection  of  Milk  at  the  Condensery. — At  the  condensery 
the  milk  is  subjected  to  rigid  inspection  by  a  man  who  is,  or 
should  be,  an  expert  on  milk  inspection ;  every  can  is  examined. 
Warm  milk  and  milk  that  is  tainted,  or  smells  slightly  sour 
should  be  rejected. 

Inspection  of  Milk  by  Sense  of  Smell  and  Taste. — In  most 
cases  the  milk  is  inspected  with  reference  to  odor.  The  inspector 
quickly  raises  the  cover  of  each  can  to  his  nostrils.  The  odor  in 
the  cover  is  typical  of  that  in  the  can.  If  it  is  "off,"  the  can- is 
rejected.  An  experienced  man  on  the  platform  can,  by  the  use 
of  this  method,  tell  with  much  accuracy,  whether  the  milk  should 
pass  or  not. 

Inspection  of  Milk  According  to  its  Temperature. — The 
temperature  is  also  noted.  This  need  not  be  done  with  the  ther- 
mometer in  each  case.  By  placing  his  hand  on  the  body  of  the 
can,  or  by  noting  the  warmth  of  the  air  and  odor  in  the  cover 
immediately  after  removing  it,  or  by  the  presence  or  absence  of 
small  particles  of  butter  floating  on  the  surface  of  the  milk,  the 
inspector  can  readily  tell  if  the  milk  has  or  has  not  been  properly 
cooled.  A  correct  thermometer  should  always  be  on  the  plat- 
form for  guidance. 

Inspection  of  Milk  by  the  Use  of  Acid  Tests. — Since  the 
degree  of  acidity,  or  the  sweetness  of  the  milk,  is  one  of  the 
chief  factors  that  determines  its  fitness  for  condensing  purposes* 
tests  that  rapidly  and  accurately  determine  the  per  cent  of  lac- 
tic acid  in  the  fresh  milk,  are  of  great  service. 

Some  concerns  have  adopted  a  definite  acid  standard  of  milk, 
rejecting  all  milk  containing  more  than  the  maximum  per  cent 
of  acid  of  their  standard,  and  they  test  every  can  of  milk  received 
with  an  acid  test.  This  method  insures  sweet  milk  in  the  fac- 


50  MILK  SUPPLY 

tory,  provided  that  the  alkaline  solutions  used  are  correct.  This 
work  involves  considerable  expense,  however,  and  unless  the 
solution  is  carefully  prepared  and  made  up  fresh  often,  its  use 
may  yield  misleading  results.  Again,  when  the  acid  test  is  per- 
formed on  the  milk  of  each  can,  the  acceptance  or  rejection  of 
the  milk  depends  altogether  on  the  per  cent  of  acid  it  contains. 
Although  milk  may  be  otherwise  unfit  for  use,  it  will  pass,  as 
long  as  it  is  low  in  acidity.  Experience  has  shown  that,  while 
it  is  necessary  for  the  condensery  to  decide  on  a  maximum  acid- 
ity of  milk  above  which  all  milk  be  rejected,  the  nose  and  the 
palate  of  the  experienced  inspector  are  better  criterions  tnan 
the  acid  test  alone,  as  to  the  fitness  of  milk  for  condensing.  Acid 
tests  are  valuable  in  the  case  of  uncertainty  and  suspicion  as 
to  the  quality  of  any  given  can  of  milk.  All  milk  containing  .18 
per  cent  lactic  acid  or  more  is  dangerous  for  condensing  pur- 
poses. 

Acid  Test  for  Daily  Use,  Where  Each  Can  of  Milk  is  Tested. 

Stock  Solution. — Weigh  out  two  hundred  grams  of  sodium 
hydrate  C.  P.  and  add  distilled  water  to  make  up  one  liter. 
Keep  tightly  stoppered. 

Solution  for  Daily  Use. — Mix  4  c.c.  of  stock  solution  with 
991  c.c.  of  distilled  water,  and  add  5  c.c.  of  phenolphthalein  indi- 
cator. The  indicator  is  prepared  as  follows :  dissolve  one  gram 
of  dry  phenolphthalein  in  100  c.c.  of  50  per  cent  alcofiol.  Each 
cubic  centimeter  of  the  prepared  alkaline  solution  neutralizes 
.01  per  cent  lactic  acid,  18  c.c.  of  the  prepared  solution,  there- 
fore, neutralize  .18  per  cent  lactic  acid,  when  a  17.6  c.c.  pipette 
is  used  for  measuring  out  the  milk. 

Making  the  Test. — With  the  Babcock  pipette,  measure  17.6 
c.c.  into  a  white  cup.  With  a  small  dipper,  holding  exactly  18 
c.c.,  pour  18  c.c.  of  the  prepared  solution  into  the  cup ;  stir  or 
shake.  If  the  mixture  remains  faintly  pink,  it  contains  less  than 
.18  per  cent  acid  and  will  pass;  if  it  turns  white,  it  contains  more 
than  .18  per  cent  acid  and  should  be  rejected  or  subjected  to  addi- 
tional tests. 

The  stock  solution  should  be  standardized  by  a  chemist. 
The  prepared  solution  should  be  made  up  daily.  Both  solutions 


MILK  SUPPLY  51 

should  be  kept  in  glass  bottles,  tightly  corked.    The  bottle  con- 
taining the  stock  solution   should  be  glass-stoppered. 

The  Boiling  Test. — Inspection  by  Heating.  The  heating  to 
the  boiling  point  of  samples  of  suspicious  milk  furnishes  a  most 
reliable  means  to  determine  the  fitness  of  such  milk  for  condens- 
ing. In  many  instances  milk  may  satisfactorily  pass  the  other 
tests  and  yet  it  may  not  be  in  condition  to  stand  the  heat  to 
which  it  will  be  subjected  in  the  process.  If  it  curdles,  when 
boiled,  it  is  obviously  unfit  for  use.  This  test  shows  more  than 
the  acid  test  above.  By  its  use  the  operator  is  able  to  detect 
milk  otherwise  abnormal,  such  as  milk  containing  colostrum,  etc., 
or  the  proteids  of  which  are  unstable  for  o-ther  reasons. 

Making  the  Test. — The  boiling  test  is  simple  and  can  be 
manipulated  rapidly.  A  sample  of  the  questionable  milk  is  taken 
into  a  small  dipper.  The  dipper  is  held  up  against  a  steam  jet 
turned  down  into  the  milk.  Direct  steam  is  turned  into  the 
milk  until  it  comes  to  a  boil.  If  flakes  or  specks  of  curd  cling 
to  the  sides  of  the  dipper,  the  milk  is  unfit  for  use. 

An  alcohol  lamp  or  gas  burner  on  the  platform  may  be  used 
for  heating  the  sample.  In  this  case  a  few  cubic  centimeters 
of  the  milk  are  discharged  with  an  ordinary  pipette  into  an  ordi- 
nary test  tube,  such  as  are  in  common  use  in  the  chemical  labo- 
ratory and  can  be  obtained  from  the  drug  store.  The  tube  is 
held  over  the  flame  and  the  milk  comes  to  a  boil  in  less  than 
a  minute.  If  the  milk  is  in  good  condition  the  sides  of  the  glass 
tube  remain  perfectly  clear.  If  it  curdles  upon  heating,  the  sides 
of  the  tube  showr  fine  specks  of  the  curd.  The  appearance  of 
these  specks  condemns  the  milk. 

In  the  case  of  milk  intended  for  evaporated  milk,  the  boiling 
test  is  not  sufficiently  severe  to  reveal  the  fitness  of  the  milk 
for  the  sterilizing  process.  For  the  reliable  detection  of  unde- 
sirable milk  for  this  purpose,  the  use  of  the  pilot  sterilizer  or  test 
sterilizer  is  recommended.  Suspicious  samples  of  milk  are  filled 
into  tins,  the  tins  are  sealed  and  placed  into  the  pilot  sterilizer 
where  they  are  given  the  same  process  of  sterilization  as  is 
used  for  the  finished  product.  Milk  that  withstands  this  sterili- 
zation can  be  depended  upon  to  also  pass  safely  through  the 
process  of  manufacture.  Milk  that  curdles  in  this  test  steriliza- 


52 


MILK  SUPPLY 


tion  obviously  shows  its  unfitness,  the  cause  of  which  should  be 
promptly  investigated  and  removed. 
Fig.  9. 

The  Sediment  Test.— This 
test  shows  the  relative  amount  of 
dirt  present  in  milk.  One-half 
pint  is  passed  through  a  small  cir- 
cle of  absorbent  cotton  and  the 
amount  of  mechanical  impurities 
present  in  the  milk  is  indicated  by 
the  color  of  the  cotton  after  filtra- 
tion. In  order  to  hasten  the  filtra- 
tion, the  milk  is  forced  through 
the  filter  under  slight  pressure; 
this  is  accomplished  by  a  rubber 
bulb  attachment  to  the  apparatus, 
as  shown  in  the  accompanying 

9  Pi*.     9 

'  '  The  sediment   tester 


Pig-.  10.     Cotton  Filters 


Clean  milk 


Dirty  milk 


If  the  cotton  retains  a  white  or  creamy  color,  the  milk  is 
relatively  free  from  filth.  Milk  .produced  under  unsanitary  con- 
ditions stains  the  cotton  brown  or  black. 

These  cotton  filters  may  be  pasted  on  a  sheet  of  paper  similar 
to  a  milk  sheet,  arranged  so  that  the  circles  are  placed  opposite 
the  respective  patron's  name  or  number.  When  shown  to  the 
patrons  who  come  to  the  factory,  they  furnish  a  most  effective 
object  lesson  to  them.  When  the  milk  reaches  the  factory  on 


MILK  SUPPLY 


53 


route  wagons  or  by  rail,  cards  similar  to.  Figure  1 1  may  be 
mailed  to  the  patrons.  The  evidence  is  so  conclusive  that  even 
the  most  obstinate  patron  cannot  help  admitting  his  guilt  and 
can  usually  be  induced  to  "clean  up."  • 


M  I  LK  COh 

IDENSING  COMPANY 
:ARD 

SEDIMENT  < 

NAME 

S        X 

/                                            \ 

/                      v 

1 

\ 

>\^                              ,/ 

THIS  IS  THE  AMOUNT  OF  DIRT   IN 
ONE  PINT  OF  YOUR  MILK 

ADDRESS 

DATE 

No. 

pigr.  11 

Fermentation  Tests. — .These  tests  are  of  great  value  in  the 
rapid  determination  of  the  kind  of  bacteria  with  which  the  milk 
from  individual  patrons  is  contaminated.  Glass  tubes  are  filled 
one-half  full  of  milk  from  each  patron.  These  tubes  are  set  in 
a  constant  water  bath  at  100  degrees  F.  and  the  changes  which 
milk  undergoes  are  noted  after  six,  twelve  and  twenty-four  hours. 

A  solid  curd  with  a  clear  whey  indicates  that  lactic  acid 
bacteria  are  the  chief  organisms  and  that  the  milk  has  been 
produced  under  cleanly  conditions.  These  organisms  are  killed 
when  the  milk  is  heated  in  the  hot  wells.  Such  milk  therefore 
is  safe,  unless  it  contains  excessive  acid,  as  shown  by  acid  test. 

A  curd  with  gas  holes,  or  that  which  is  torn  to  pieces  in  the 
tubes,  shows  the  presence  of  gas-producing  germs.  These  come 
largely  from  manure  and  other  filth.  Among  these  are  Bacillus 
coli  communis,  the  natural  inhabitant  of  the  colon  of  the  animal, 
and  butyric  acid  organisms  which  are  spore  bearers.  The  latter 
especially  may  give  rise  to  serious  milk  defects,  causing  "swell 


54  FACTORY  SANITATION 

heads."  Patrons  sending  such  milk  should  be  looked  after  at 
once. 

If  the  curd  dissolves,  or  no  curd  is  formed  and  the  milk 
changes  into  a  transparent  liquid,  it  usually  is  contaminated  by 
germs  from  the  dust  of  hay  and  bedding,  or  polluted  water.  To 
this  class  of  organisms  belong  Bacillus  subtilis,  Bacillus  fluores- 
cens  liquifaciens,  Plectridium  foetidiim,  Bacillus  putrificus,  etc. 
Some  of  these  are  violent  gas  producers  and  most  of  them  are 
spore-bearers.  They  are  the  cause  of  the  most  disastrous  milk 
defects.  Dairies  from  which  such  milk  comes  should  be  vigor- 
ously inspected  and  all  milk  from  them  should  be  rejected,  until 
the  patrons  have  learned  how  to  furnish  sanitary  milk. 

Milk  that  remains  unchanged  for  twenty-four  hours  when 
subjected  to  the  fermentation  test,  suggests  that  it  contains  some 
preservative.  It  is  possible,  however,  for  milk  produced  under 
ideally  sanitary  conditions  to  remain  normal  and  unchanged  even 
at  these  high  temperatures  for  several  days.  Where  milk  comes 
to  the  factory  in  bulk  as  is  the  case  in  the  condensery,  samples 
showing  abnormal  keeping  quality  should  be  regarded  with  sus- 
picion, and  the  respective  dairies  should  receive  immediate  and 
thorough  inspection. 

Tests  for  Butterfat  and  Specific  Gravity. — In  the  factories 
where  the  milk  is  not  paid  for  on  the  butterfat  basis,  composite 
samples  should  be  taken  daily,  to  be  tested  for  fat  and  specific 
gravity,  at  regular  intervals  of  from  two  to  four  weeks,  in  order 
to  detect  possible  adulterations  by  skimming  or  by  the  addition 
of  water.  For  specific  directions  for  the  Babcock  test, 'the  use  of 
the  lactometer  and  tests  for  preservatives  see  Chapter  XXX 
" Chemical  Tests  and  Analyses  of  Milk  and  Milk  Products." 

FACTORY  SANITATION. 

In  the  previous  paragraphs,  special  emphasis  was  placed  on 
the  great  importance  of  a  good  quality  of  fresh  milk.  It  is  equally 
essential  that  the  factory  be  kept  in  exemplary  condition  as  to 
cleanliness  and  sanitation.  This  is  necessary  because  of  its  effect 
on  the  ;patrons  and  on  the  wholesomeness  and  marketable  prop- 
erty of  the  finished  product. 

Effect  on  Patrons. — It  does  not  take  the  watchful  eye  of  the 
intelligent  patron,  who  daily  comes  to  the  factory,  very  long  to 


FACTORY  SANITATION  55 

learn,  whether  the  manufacturer  gives  his  milk  as  good  care  as 
he  gave  it  on  the  farm.  A  good  example  set  by  the  factory  will 
mean  much  toward  instilling  the  patron  with  ambition  to  do 
likewise  on  the  farm.  Shiftlessness  is  a  contagious  disease,  to 
which  the  average  farmer  is  very  susceptible.  It  is,  therefore, 
inconsistent  for  the  factory  to  issue  and  enforce  rules  of  sanitation 
for  the  dairy  farmer  when,  within  its  own  walls,  all  principles 
of  sanitation  are  violated. 

Effect  on  Wholesomeness  of  the  Product. — Uncleanliness 
and  filth  interfere  with  the  wholesomeness  of  the  product.  Con- 
densed milk  made  in  a  factory  ignoring  sanitation,  may  contain 
certain  products  of  decay  which  are  poisonous  to  the  human 
system.  Again,  it  may  contain  germs  of  infectious  diseases  and 
thus  become  the  cause  of  widespread  epidemics  of  these  diseases 
and  possibly  claim  many  victims.  As  a  matter  of  common  decency 
and  of  duty  to  the  commonwealth,  the  condensery  should  pay 
close  attention  to  cleanliness  in  all  operations. 

Effect  on  the  Marketable  Property  of  the  Product. — Again, 
uncleanliness  in  the  factory  is  bound  to  bring  financially  dis- 
astrous results.  The  seriousness  of  the  disaster  is  greatly  aug- 
mented by  the  fact  that  the  consequences  of  neglect  are  usually 
not  apparent  until  after  the  goods  have  reached  the  market.  The 
pollution  of  condensed  milk  with  impurities  and  filth  in  the 
factory,  shortens  the  life  of  the  product  Such  condensed  milk 
is  of  very  poor  keeping  quality.  It  may  reach  the  market  and  the 
consumer  in  condition  that  causes  it  to  be  rejected,  resulting  in 
a  complete  loss  to  the  manufacturer.  The  manufacturer  allowing 
such  conditions  to  exist,  is  usually  the  last  man  to  realize  and 
admit  that  he  is  at  fault,  which  renders  attempts  to  locate  and 
stop  such  defects  exceedingly  difficult.  Furthermore,  instead 
of  helping  to  build  up  the  trade  and  to  advertise  the  brand,  he 
demoralizes  it. 

How  to  Keep  Factory  in  Sanitary  Condition. — Cleanliness 
in  the  factory  is  absolutely  essential.  The  milk  vats  should  be 
rinsed  with  plenty  of  water  and  scrubbed  and  steamed  thor- 
oughly, as  soon  as  possible  after  use.  The  copper  kettles  and 
vacuum  pans  should  be  rinsed,  then  scoured  with  sandpaper  or 
emery  cloth,  then  rinsed  and  steamed  thoroughly.  The  milk 
pipes  should  be  scoured  by  running  flue  brushes  through,  flush- 


56  FACTORY  SANITATION 

ing  them  with  clean  water  and  steaming  them  until  they  are 
scalding  hot.  In  the  case  of  milk  pipes  of  excessive  length,  they 
should  be 'well  flushed  with  hot  alkaline  water.  Milk  pumps 
should  be  taken  apart  every  day  and  freed  thoroughly  from  all 
remnants  of  milk.  The  water  in  the  cooling  tanks  should  be 
changed  as  often  as  is  necessary  to  insure  clean  water  in  them 
at  all  times.  The  homogenizer  should  receive  special  attention, 
all  its  valves  should  be  thoroughly  cleaned  and  steamed  daily. 
The  cooling  coils  should  be  scalded  before  use.  The  filling 
machines'  for  evaporated  milk  should  be  freed  from  all  milk, 
rinsed  and  steamed  thoroughly  and  no  remnants  of  milk  should 
be  allowed  to  stick  to  the  valves.  The  filling  machines  for 
sweetened  condensed  milk  should  be  emptied  and  completely 
washed,  at  least  once  per  week,  and  protected  from  dust  and  flies 
by  covering  them  Avhen  riot  in  use.  The  tin  cans  should  be  stored 
in  a  clean  room  and  every  precaution  should  be  taken  to  guard 
against  their  defilement  from  dirt,  dust,  insects  and  mice.  Where 
possible  they  should  be  sterilized  before  use. 

All  vats,  kettles,  milk  conveyors,  vacuum  pans,  milk  pumps, 
and  all  machinery  coming  in  contact  with  milk,  should  be  flushed 
and  steamed  again  in  the  morning,  as  soon  as  the  condensery 
opens.  The  sugar  chute  should  be  kept  clean,  care  being  taken 
that  no  damp  or  wet  sugar  remains  in  it.  Special  attention  should 
be  given  to  the  washing  of  the  farmers'  cans.  After  washing 
with  brush  and  hot  water  containing  some  good  washing  powder, 
they  should  be  thoroughly  rinsed,  then  steamed  until  they  are 
hot.  If  possible  they  should  be  dried  by  an  air  blast. 

'The  floors  and  walls  of  the  factory  should  be  kept  in  sanitary 
condition.  Accumulated  rubbish  should  be  removed  and  sewers 
and  drains  should  be  disinfected  at  regular  intervals. 

Can  Washing. — Another  extremely  important,  and  often 
woefully  neglected  feature,  relating  to  the  effective  management 
of  the  patron  from  the  standpoint  of  high  quality  of  milk,  is  the 
condition  of  the  milk  cans  which  the  factory  returns  to  the  patron. 

The  patron  is  bound  to  lose  his  .interest  in  taking  painstaking 
care  of  his  milk  when  the  cans  returned  to  him  by  the  factory  are 
filthy  and  foul-smelling.  Nor  need  the  factory  expect  the  milk, 
it  receives  in  such  cans,  to  be  either  of  high  quality  for  condens- 
ing or  wrholesome.  And  yet  an  astounding  proportion  of  con- 


FACTORY  SANITATION  57 

densery  cans  reach  the   farmer  in  condition,  unfit  to  receive  and 
ship  milk  in. 

Proper  can  washing  consists  of  four  essential  operations, 
namely,  washing,  rinsing,  steaming  and  drying. 

The  cans  should  be  washed  until  all  remnants  of  milk  are 
removed.  They  should  be  rinsed  with  hot  water  until  all  of  the 
dirty  wash  water  is  flushed  out.  They  should  be  steamed  until 
"piping-hot,"  and  they  should  be  dried  until  "bone-dry." 

There  is  IIOAV  admirable  equipment  available  on  the  market 
for  accomplishing  these  four  important  purposes,  affording  ade- 
quate facilities  to  enable  the  condensery  to  return  to  the  patron 
cans  that  are  clean,  sterile  and  dry. 

Care  of  Milk  in  the  Factory  Prior  to  Manufacture. — The 
problem  of  so  handling  the  milk  in  the  factory,  from  the  time  it 
arrives  until  it  is  heated  preparatory  to  evaporation,  is  an  im- 
portant one,  that  has  received  much  careful  consideration  by  the 
foremost  condensed  milk  men.  Since  bacteriological  analyses 
have  shown  that,  under  favorable  temperature  conditions,  the 
micro-organisms  present  in  milk  are  capable  of  doubling  in 
number  once  every  twenty  minutes,  it  is  essential  that  the  milk 
either  be  Heated  to  high  enough  temperatures  to  restroy  germ 
life,  or  be  cooled  to  a  temperature  low  enough  to  stop  growth 
and  multiplication,  as  soon  as  possible. 

Both  practices  are  feasible,  but 
to  heat  the  large  volumes  of  milk  that 
arrive  at  the  factory,  all  within  a  few 
hours,  would  tax  the  equipment  of  the 
factory  under  average  conditions  very 
heavily.  And  unless  the  condensery 
were  equipped  with  very  large  vacu- 
um pan  capacity,  much  of  this  heated 
milk  would  have  to  lie  idle  in  the 
forewarmers  for  hours,  avaiting  its 
12.  turn  for  condensation.  This  would 

Glass-lined    tank    for    cooling   be  undesirable  and  might  prove  harm- 

and   holding1   milk   before 

manufacture  ful    to    the    quality    of    the    finished 

Courtesy  of  The  Pfaudler  Co.      product 

Efforts  have,  therefore,  been  made,  especially  within  recent 
years,  to  provide  a  practical  and  economical  method  of  cooling 


58  FACTORY  SANITATION 

the  milk  as  soon  as  it  arrives  and  of  holding  it  at  a  low  tempera- 
ture until  ready  for  heating  and  condensing.  This  has  led  to 
diverse  practices,  such  as  running  the  milk  over  a  surface  coil 
cooler  into  a  jacketed  tank,  or  cooling  it  by  running  it  into  a 
large  tank  equipped  with  cold  air  blowers,  or  cooling  the  milk  in 
large  vats  equipped  with  revolving  coils,  etc. 

One  of  the  later  methods  for  refrigerating  the  milk  consists 
of  the  use  of  large,  usually  circular,  glass  enameled  steel  tanks. 
These  tanks  are  completely  surrounded  on  their  sides  and  bottom 
by  a  cold  water  or  brine  jacket  and  are  equipped  with  a  milk 
distributing  device  that  causes  the  inflowing  milk  to  be  sprayed 
by  gravity  against  the  top  of  the  sides  of  the  tank  and  to  per- 
colate in  a  thin  layer  down  the  sides.  In  this  manner  the  cooling 
is  instantaneous,  the  entire  sides  of  the  tank  being  surrounded 
by  the  cooling  medium.  It  is  aimed,  to  cool  the  milk  to  about 
40  to  45  degrees  F.  and  to  hold  it  at  this  temperature  until  ready 
for  manufacture. 

These  glass  enameled  tanks  have  many  advantages ;  they 
minimize  the  initial  cost  of  the  necessary  equipment,  reducing 
the  number  of  costly  vacuum  pans,  and  forewarmers,  required ; 
they  cut  down  labor  cost,  because  they  reduce  the  equipment  to 
fewer  pieces  to  operate  arid  to  clean ;  they  are  of  such  construc- 
tion that  they  are  easily  and  quickly  cleaned  and  readily  kept  in 
proper  sanitary  condition,  the  smooth  and  pore-free  enamel  yields 
more  readily  to  the  brush  than  copper  surfaces ;  they  avoid  all 
possibility  of  chemical  action  of  the  milk  on  metal  and,  therefore, 
are  a  reliable  safeguard  against  the  development  of  metallic 
flavor  in  the  milk. 

The  use  of  these  large  holding  tanks  also*  facilitates  the 
standardization  of  the  milk  for  fat  and  solids  not  fat.  For  detailed 
directions  on  standardizing  see  Chapter  XXIX. 


PART  II. 

MANUFACTURE  OF  SWEETENED 
CONDENSED    MILK 

CHAPTER  IV. 

DEFINITION. 

Sweetened  condensed  milk  is  cow's  milk,  condensed  at  the 
ratio  of  2%  to  2%  parts  of  fresh  milk  to  1  part  condensed  milk. 
It  contains  considerable  quantities  of  sucrose,  usually  about 
40  per  cent,  to  preserve  it.  It  is  of  semi-fluid  consistency  and 
reaches  the  market  in  hermetically  sealed  tin  cans,  varying  in 
size  from  eight  ounces  to  one  gallon,  and  in  barrels  similar  to 
glucose  barrels,  holding  from  three  hundred  to  seven  hundred 
pounds  of  condensed  milk.  When  made  properly,  sweetened 
condensed  milk  will  keep  for  many  months,  but  is  best  when 
fresh. 

HEATING. 

Purpose. — The  first  step  in  the  process  is  to  heat  the  milk  to 
near  the  boiling  point.  There  are  three  chief  reasons  for  which 
the  milk  is  heated,  namely,  to  destroy  most  of  the  bacteria,  yeast, 
molds  and  other  organized  and  unorganized  ferments,  to  facilitate 
the  solution  of  the  sucrose,  and  to  prevent  the  milk  from  burning 
on  to  the  heating  surface  in  the  vacuum  pan. 

Destruction  of  Ferments. — When  the  fresh  milk  arrives  at 
the  factory  it  contains  micro-organisms  in  varying  numbers  and 
of  different  species.  In  some  cases  disease-producing  bacteria 
may  be  present,  rendering  the  milk  dangerous  to  the  health  and 
life  of  the  consumer,  were  it  not  heated  to  temperatures  high 
enough  to  destroy  these  germs.  Again,  milk  may  contain  bac- 
teria, yeast,  molds  and  enzymes  that  cause  it  to  undergo  un- 
desirable fermentations  which,  if  allowed  to  pass  into  the  con- 
densed milk,  may  tend  to  shorten  the  life  and  impair  the  whole- 
someness  and  marketable  properties  of  the  latter. 


60  SWEETENED  CONDENSED  MILK — HEATING 

Solution  of  Sucrose. — It  is  very  essential  that  all  the  cane, 
sugar  which  is  added  to  the  milk  be  completely  dissolved,  -in 
order  to  lessen  the  tendency  of  the  sugar  to  form  large  crystals 
in  the  finished  product.  Undissolved  sugar  crystals  in  condensed 
milk  act  in  a  physical  way  much  as  bacteria  in  fluid  milk  do  in  a 
bacteriological  way.  They  multiply  rapidly,  and  such  condensed 
milk  usually  precipitates  its  sugar  before  the  product  reaches 
the  market.  The  presence  of  excessively  large  sugar  crystals 
makes  the  product  gritty  and  causes  the  formation  of  a  sediment 
in  the  bottom  of  the  cans;  this  is  objectionable  to  the  consumers. 
When  the  milk  is  heated  to  the  proper  temperature  before  con- 
densing, the,  solution  of  the  cane  sugar  is  facilitated  and  the 
tendency  toward  grittiness  is  minimized. 

Prevention  of  Burning  Milk  on  Heating  Surface. — If  cold 
milk  comes  in  contact  with  a  steam-heated  surface  and  is  not  agi- 
tated vigorously,  it  bakes  or  burns  onto  this  heating  surface.  The 
milk  in  the  vacuum  pan  is  heated  or  kept  hot  by  means  of  the 
steam  jacket  and  coils.  These  radiators  are  charged  with  steam 
under  pressure  and  consequently  give  off  a  high  degree  of  heat. 
If  cold  milk  is  drawn  into  the  vacuum  pan,  the  milk  remains 
calm  for  a  considerable  length  of  time.  During  this  time  it  is 
bound  to  bake  or  burn  on  the  heating  surface,  giving  the  product 
a  burnt  flavor,  causing  it  to  contain  brown  specks  and  retarding 
the  process  of  evaporation.  If  the  milk  is  hot  when  it  enters  the 
pan,  the  reduced  pressure  in  the  pan  causes  it  to  boil  violently  at 
once,  avoiding  all  danger  of  sticking  to  and  burning  on  the  heat- 
ing surface  and  making  possible  maximum  rapidity  of  evapora- 
tion. 

Temperature. — In  most  factories  the  milk -is  heated  to  from 
180  degrees  F.  to>  200  degrees  F.  This  temperature  is  sufficient 
to  accomplish  the  three  purposes.  Heating  the  milk  to  the 
b6iling  point  tends  to  give  it  a  rather  pronounced  cooked  flavor, 
which  is  objectionable.  However,  in  the  case  "of  danger  of  con- 
tamination of  the  milk  with  resistant  types  of  undesirable  bac- 
teria, it  may  become  necessary  to  practice  boiling  the  milk. 

Manner  of  Heating. — Thorough,  efficient  and  rapid  heating 
of  large  volumes  of  milk  to  temperatures  near  the  boiling  point 
is  a  problem  that  requires  careful  consideration.  The  tendency 


SWEETENED  CONDENSED  Miwc — HEATING 


61 


of  the  milk  to  stick  to  the  heating  surface  is  a  permanent  obstacle 
and  efforts  to  overcome  this  frequently  result  in  sacrificing  thor- 
oughness of  heating. 

A  variety  of  methods  and  numerous  different  types  of  ma- 
chines are  used  for  this  purpose  in  the  different  milk  condensing 
factories.  Some  use  large  copper  kettles  in  which  the  milk  is 
heated  by  turning  ste.am  direct  into  the  milk.  Others  use.  jacketed 
copper  kettles  equipped  with  a  revolving  agitator.  The  milk  is 

heated  by  turning  steam  under 
pressure  into  the  jacket  and  the 
burning  of  the  milk  is  prevented  by 
keeping  the  milk  in  constant  motion. 
In  this  case  the  milk  is  usually 
heateji  to  about  170  degrees  F.  by 
the  jacket  and  from  there  on  the 
temperature  is  raised  to  that  desired, 
by  turning  steam  direct  into  the  hot 
milk.  Still  others  are  heating  the 
milk  by  means  of  large  continuous 
pasteurizers  in  which  case  hot  water 
or  steam  serves  as  the  heating  medi- 
um. The  milk  passes  in  a  thin  layer 
between  two  water-heated  surfaces, 
one  of  which  is  revolving.  In  some 
factories  the  milk  is  forced  through  a  series  of  pipes  inclosed  in 
a  hot  water  or  steam  jacket. 

Finally,  in  some  condenseries  a  combination  of  the  con- 
tinuous pasteurizer  and  the  plain  or  jacketed  kettle  is  used.  The 
milk  is  heated  to  nearly  the  desired  temperature  in  the  pasteur- 
izer. From  there  it  flow's  into  the  kettle,  where  the  heating  is 
completed.  This  method  insures  efficient  heating  and,  at  the 
same  time,  if  operated  properly,  it  prevents  scorching  of  the 
milk  on  the  heating  surface. 

Advantages  and  Disadvantages  of  Different  Methods  of 
Heating. — In  most  factories  in  this  country  the  first  named 
method  is  used.  Steam  is  turned  direct  into  the  milk  until  it 
boils  up.  This  is  the  oldest  and  most  primitive  method.  While 
very  simple  in  operation,  this  method  has  some  objections.  At 


Figf.   13. 
The  hot  well  or  forewarmer 

Courtesy  of  Arthur  Harris  &  Co. 


62 


CONDENSED   MlLK — HEATING 


best,  much  of  the  steam  used  condenses  in  the  milk,  increasing 
the  amount  of  water  that  has  to  be  evaporated.  It,  therefore, 
prolongs  the  process  of  condensing  and  increases  the  cost  of 
manufacture.  This  is  especially  true  where  the  boilers  are 
located  at  some  distance  from  the  hot  wells  and  the  steam  pipes 
are  not  well  insulated,  causing  the  steam  to  be  "wet,"  and  when 
the  milk  to  be  heated  is  cold.  It  is  estimated  that  the  amount 
of  extraneous  water  thus  added  to  the  milk  increases  the  bulk 
of  the  milk  by  about  one-sixth  of  its  original  volume.  The  steam 
is  often  associated  with  impurities,  such  as  cylinder  oil  from 
the  engine,  boiler  compounds  used  in  the  boilers,  scales  from  the 
inside  of  the  pipes,  etc.  These  various  impurities  cannot  possbily 
improve,  but  may  seriously  injure  the  quality  of  the  milk.  It  is 
generally  conceded  by  those  who  have  given  this  matter  careful 


Fig-.  14.     Steam  rosette  for  heating*  milk 

Courtesy  of  Arthur  Harris  &  Co. 

thought,  that  the  turning  of  steam  direct  into  the  milk  shortens 
the  life  of  the  product  and  causes  it  to  develop  a  stale  flavor, 
which  may  degenerate  into  an  oily  flavor.  The  same  defect  is 
noted  also  when  cream  is  heated  by  turning  steam  into  it.  The 
prolonged  exposure  of  the  milk  to  the  condensing  process,  as  the 
result  of  the  addition  to  the  milk  of  considerable  quantities  of 
condensed  steam,  is  an  additional  objection. 

From  the  above  discussion  it  is  obvious  that  the  heating  of 
the  milk  by  bringing  it  in  direct  contact  with  free  steam  has 
some  objections.  Just  to  what  extent  this  practice  jeopardizes 
the  quality  has  not  been  very  conclusively  demonstrated.  But 
it  is  recommended  that  the  heating  with  direct  steam,  if  it  must 
be  practised,  be  confined  to  the  last  stages  of  the  heating  process, 


CONDENSED  MILK — ADDITION  OF  SUGAR         63 

that  is,  that  the  milk  be  heated  to  pasteurizing  temperature, 
170  degrees  F.  or  thereabout,  by  the  use  of  a  continuous  pas- 
teurizer, or  a  jacketed  kettle,  or  other  similar  means,  and  that 
from  there  on  only  to  the  desired  temperature,  direct  steam  be 
used. 

ADDITION  OF  SUGAR. 

Considerable  quantities  of  sucrose  are  added  to  the  con- 
densed milk  for  the  purpose  of  preserving  it. 

Kinds  of  Sugar. — In  order  to  convey  to  the  milk  preservative 
properties,  that  kind  of  sugar  must  be  used  which  does  not  readily 
undergo  fermentation  and  which  has  the  power  of  inhibiting  bac- 
terial activity  when  dissolved  in  a  concentrated  solution.  Glucose 
could  be  purchased  at  a  very  low  cost,  but  it  is  not  suitable  for 
this  purpose,  since  it  is,  in  itself,  very  unstable  and  fermentable. 
It  has  no  preservative  qualities,  even  in  concentrated  solutions. 
Sucrose,  saccharose,  or  cane  sugar,  Cl2R22Ollf  properly  refined, 
ferments  with  difficulty  in  concentrated  solutions,  and  has  the 
power  of  retarding  the  growth  of  bacteria  and  other  ferments 
ordinarily  present  in  sweetened  condensed  milk.  It  is,  therefore, 
very  satisfactory  and  useful  in  this  connection. 

Beet  sugar,  which  is  chemically  indentical  with  cane  sugar, 
is  used  in  European  countries  very  largely  in  the  place  of  cane 
sugar.  On  the  continent  the  beet  sugar  industry  is  an  important 
factor.  With  the  climate  adapted  to  the  growing  of  sugar  beets 
and  the  labor  relatively  cheap,  beet  sugar  can  be  secured  by  the 
European  condenseries  at  lower  cost  than  cane  sugar.  In  America, 
where  the  annual  sugar  cane  crop  is  large  and  where  the  high 
cost  of  labor  renders  the  expense  of  growing  sugar  beets  relative^ 
ly  high,  there  is  practically  no*  difference  between  the  price  of 
cane  sugar  and  beet  sugar.  When  American  beet  sugar  was 
used  in  the  condenseries  during  the  infancy  of  the  beet  sugar 
industry,  this  sugar  was  found  undesirable,  often  giving  rise  to 
fermented  condensed  milk.  It  was  then  supposed  by  the  con- 
densed milk  men  that  beet  sugar  contained  very  resistant  spore- 
bearing  bacteria,  which  followed  the  beets  from  the  soil  into  the 
refined  sugar.  This  conclusion  is  highly  improbable,  as  the 
temperatures  and  chemicals  employed  in  the  process  of  beet 
sugar  making  are  prohibitive  of  the  passage  of  living  bacteria 


64  SWSUTENSD   CONDENSED    MlI,K  —  ADDITION    OF    SUGAR 


from  the  soil  to  the  finished  sugar.  It  is  possible,  however,  that 
the  standard  of  refinement  of  American  beet  sugar,  during  the 
earlier  days  of  its  manufacture,  was  low  and  that  some  of  the 
beet  sugar  on  the  market  may  have  contained  small  amounts  of 
acid,  invert  sugar  and  other  impurities,"  ingredients  of  such  a 
nature  as  to  render  the  sugar  prone  to  give  rise  to  fermentation 
and,  therefore,  condemn  its  use  in  the  milk  condensery. 

While  the  beet  sugar  on  the  market  today  appears  to  have 
reached  a  very  high  state  of  refinement  and  is,  according  to  the 
best  authorities,  equal  in  purity  to  cane  sugar,  it  is  still  shunned 
by  the  American  condenseries,  which  insist  that  nothing  but 
cane  sugar  will  do.  However,  whenever  a  shortage  occurs  of  the 
sugar  cane  crop  in  the  West  Indies,  raw  European  beet  sugar  is 
imported  into  the  United  States  and  it  all  emerges  from  our  sea- 
board refineries  as  "pure  cane  sugar."  It  is  not  improbable,  there- 
fore, that  the  sugar  supply  of  many  American  condenseries  today 
consists  at  times  largely  of  beet  sugar,  though  it  is  purchased 
under  the  name  of  cane  sugar. 

There  is  no  good  reason  why  the  best  refined  beet  sugar, 
manufactured  today  in  this  country  and  elsewhere,  should  not 
give  fully  as  good  results  for  condensing  purposes  as  the  same 
quality  of  cane  sugar.  Tests  made  at  the  California  Agricultural 
Experiment  Station1  led  to  the  conclusion  that  the  two  kinds 
of  sugar,  cane  sugar  and  beet  sugar,  were  equally  valuable  for 
canning  and  identical  in  their  behavior  when  of  the  same  fineness 
of  crystallization. 

Beet  Sugar  Cannot  be  Detected  from  Cane  Sugar.  —  While 
the  raw  sugar  from  the  two  different  sources,  the  sugar  cane 
and  the  sugar  beet,  takes  on  the  character  of  the  impurities  from 
which  it  has  not  yet  been  freed  (the  raw  product  of  the  sugar 
cane  is  pleasant  in  flavor,  the  raw  product  from  the  sugar  beet 
is  acrid  and  disagreeable  in  flavor),  the  sucrose  or  so-called  pure 
cane  sugar,  can  be  and  is  crystallized  out,  and  in  every  case  the 
sugar  is  identical  in  chemical  composition,  appearance  and  prop- 
erties. "By  no  chemical  test  can  the  pure  crystallized  sugar 
from  these  two  different  sources  be  distinguished."2 

1  California  Agricultural  Experiment  Station,  Circular  No.  33. 

2  United   States    Department   of   Agriculture,    Farmers'    Bulletin    No.    535, 
1913. 


CONDENSED  MILK — ADDITION  OF  SUGAR         65 

Quality  of  the  Sugar. — Since  the  sugar,  sucrose,  is  added  for 
the  purpose  of  preserving  the  condensed  milk,  it  is  obvious  that 
none  but  the  best  quality  of  refined  sucrose  is  admissible.  Low 
grade  sucrose  is  a  product  dangerous  to  the  condensed  milk 
business.  It  is  apt  to  contain  sufficient  quantities  of  acid  and 
invert  sugar,  to  give  bacteria  and  yeast  an  opportunity  to  start 
fermentation.  When  once  started,  the  destruction  of  the  product 
is  almost  inevitable.  In  years  of  failure  of  the  cane  sugar  crop, 
when  the  prices  of  sucrose  soar  high,  condenseries  yield  frequent- 
ly to  the  temptation  of  buying  lower  grades  of  sugar.  The  result 
invariably  is  an  abnormally  large  output  of  condensed  milk  that 
"goes  wrong." 

It  is  very  important  that  the  sugar  in  the  iactory  be  stored 
where  it  will  keep  dry.  Sucrose  has  hygroscopic  properties. 
When  exposed  to  an  atmosphere  saturated  with  moisture  it  ab- 
sorbs water.  In  damp  storage  it  is  prone  to  become  lumpy, 
moldy  and  frequently  sour.  When  these  precautions  are  neglected 
there  is  danger  of  defective  condensed  milk,  causing  the  cans  on 
the  market  to  swell,  due  to  gaseous  fermentation. 

Adulteration  of  sugar  with  foreign  admixtures,  such  as  white 
sand,  white  clay,  starch,  or  lime  dust  is  rare,  and  occurs  usually 
only  in  pulverized  sugar.  For  the  detection  of  these  adulterants, 
add  a  spoonful  of  the  suspicious  sugar  to  a  glass  of  hot  water 
and  stir.  Pure  sugar  will  dissolve  completely,  while  most  of  the 
common  impurities  are  insoluble  and  will  settle  to  the  bottom. 

The  purchase  of  coarsely  granulated  sugar  is  an  effective 
safeguard,  insuring  freedom  from  these  adulterants.  Powdered 
sugar  should  not  be  used  in  the  condensery. 

Amount  of  Sugar. — The  amount  of  sucrose  used  varies  in 
different  countries,  with  different  manufacturing  concerns,  in 
different  factories  of  the  same  company  and  at  different  seasons 
of  the  year.  The  normal  variations  range  between  twelve  and 
eighteen  pounds  of  sucrose  per  one  hundred  pounds  of  fresh 
milk.  Most  factories  use  about  16  per  cent. 

It  is  not  advisable  to  overstep  the  limits  above  indicated. 
Condensed  milk  serves  as  a  substitute  for  fresh  milk.  The  more 
sucrose  it  contains,  the  greater  is  the  difference,  in  composition 
and  properties  between  the  condensed  milk  and  the  fresh  milk. 


66         SWEETENED  CONDENSED  MILK — ADDITION  OF  SUGAR 

Sucrose  is  not  as  readily  digested  as  the  other  ingredients  of 
milk ;  therefore,  the  presence  of  excessive  amounts  of  cane  sugar 
in  condensed  milk  tends  to  reduce  its  digestibility  and  its  whole- 
someness  as  a  food.  Again,  while  normal  milk  is  a  well-balanced 
food  in  itself,  the  presence  of  large  amounts  of  cane  sugar  in 
it  causes  this  equilibrium  to  be  disturbed,  the  condensed  milk 
being  excessively  rich  in  carbohydrates  and  relatively  poor  in 
proteids.  These  facts  are  specially  significant  where  condensed 
milk  is  used  for  infant  feeding  and  by  persons  with  weak 
digestion. 

On  the  other  hand,  sweetened  condensed  milk  depends  for  its 
preservation  on  the  sucrose.  This  class  of  condensed  milk  is  not 
sterile  and  is  prevented  from  rapipd  deterioration  by  the  pre- 
servative action  of  the  sucrose  only.  Therefore,  the  smaller  the 
amount  of  sucrose  it  contains,  the  greater  the  danger  from  the 
activity  of  ferments  and  the  lower  its  keeping  quality. 

The  relative  prices  of  cane  sugar  and  of  fresh  milk  also 
govern  the  amount  of  cane  sugar  used  in  many  factories.  In 
summer,  milk  prices  are  low  and  sugar  prices  are  high,  while  in 
winter  the  relative  prices  are  reversed.  Hence  there  is  a  tendency 
on  the  part  of  the  manufacturer  to  use  less  sugar  in  summer  than 
in  winter. 

'.'•  Again,  the  amount  of  cane  sugar  used  varies  according  to 
the  kind  of  market  for  which  the  condensed  milk  is  intended. 
Milk  put  on  the  market  in  hermetically  sealed  cans  is  generally 
exposed  to  more  unfavorable  conditions  and  is  older  by  the  time 
it  reaches  the  consumer  than  milk  sold  in  barrels.  It  is  customary 
to  use  about  sixteen  pounds  of  cane  sugar  for  every  one  hundred 
pounds  of  fresh  milk  for  canned  goods,  and  about  twelve  to  four- 
teen pounds  of  cane  sugar  for  barrel  goods. 

Finally,  there  is  a  strong  tendency  in  some  localities  for 
sweetened  condensed  milk  made  in  May  and  June,  to  thicken 
rapidly  and  become  cheesy  with  age.  This  can  easily  be  prevented 
by  the  use  of  more  cane  sugar  in  the  milk  manufactured  during 
these  months.  (See  Chapter  XXII  on  "Condensed  Milk 
Defects/') 

A  more  accurate  method  of  determining  the  amount  of  sugar 
that  should  be  added  to  the  original  milk  in  order  to  secure  a 


CONDENSED  MILK — ADDITION  OF  SUGAR         67 

definite  desired  percentage  of  cane  sugar  in  the  finished  product, 
is  to  accurately  test  and  standardize  the  original  fluid  milk  for 
fat  and  solids  not  fat  and  then  calculate  the  pounds  of  sugar  to  be 
added  on  the  basis  of  the  total  pounds  of  fat  or  of  solids  present. 
For  detailed  directions  see  Chapter  XXIX  on  " Standardization." 

Mixing  the  Sugar. — The  "sugar  is  added  to  the  hot  milk  be- 
fore the  latter  enters  the  vacuum  pan.  In  some  factories  a 
separate  tank  is  provided  for  this  purpose.  Small  portions  of 
the  hot  milk  are  allowed  to  flow  into  this  tank.  To  these  the 
sugar  is  added.  This  tank  is  called  the  sugar  well.  It  is  usually 
equipped  with  a  mechanical  reversible  stirrer,  moving  to  and  fro 
on  an  eccentric,  to  facilitate  the  solution  of  the  sugar.  The  milk 
from  the  heater  and  from  the  sugar  well  runs  into  a  tank  sunk 
into  the  floor  of  the  well  room,  the  ground  well,  from  which  the 
mixed  sweetened  milk  is  drawn  into  the  vacuum  pan.  In  other 
factories  the  sugar  well  and  ground  well  are  one  and  the  same 
tank,  into  which  the  milk  runs  direct  from  the  heater.  In  this 
case  it  is  advisable  to  set  a  wire  mesh  strainer  (sixty  to  eighty 
meshes  to  the  inch)  over  the  sugar  well.  The  sugar  is  placed 
into  this  strainer,  a  little  at  a  time ;  the  hot  milk  from  the  heater 
passing  into  and  through  the  strainer  dissolves  the  sugar.  A 
paddle  or  stick  should  be  used  to  stir  the  sugar  in  the  strainer. 
For  greater  convenience  and  economy  of  labor,  the  sugar  barrels 
and  scales  are  placed  on  the  floor  over  the  well  room.  The 
sugar  is  transferred  to  the  strainer  below  through  a  sugar  chute 
which  may  be  equipped  at  the  lower  end  with  an  adjustable  cut- 
off to  regulate  the  sugar  coming  down.  Or  the  kettles,  hot 
wells  or  sugar  wells  in  which  the  sugar  is  added  to  the  milk, 
are  sunk  into  the  floor  sufficiently  to  facilitate  the  emptying  of 
the  sugar  barrels  direct  from  the  floor  into  the  milk.  In  this 
case  no  sugar  chute  is  needed.  Other  factories  dissolve  their 
sugar  in  boiling  water  in  a1  separate  tank,  and  draw  this  syrup 
into  the  vacuum  pan  together  with  the  hot  milk.  This  is  a  very 
commendable  practice,  as  it  minimizes  the  danger  of  undissolved 
sugar  crystals  escaping  into  the  pan.  Moreover,  this  watery 
syrup  can  be  boiled  without  danger  of  giving  the  milk  a  cooked 
flavor, 


68 


SWEETENED  CONDENSED  MILK — CONDENSING 


CHAPTER  V. 
CONDENSING. 

From  the  ground  well  in  the  well  room  the  sweetened  milk 
is  drawn  into  the  vacuum  pan,  where  it  is  condensed  under 
reduced  pressure.  The  vacuum  pan  is  usually  located  on  the 
second  floor  over  the  well  room,  or  in  the  well  itself,  in  which 
case  it  is  elevated  above  the  floor  six  to  eight  feet.  The  vacuum 
pan  is  connected  with  the  vacuum  pump,  which  should  be  in- 
stalled near  the  pan. 

Description  of  the  Vacuum  Pan. 
—The  vacuum  pan  is  a  retort  in 
which  the  milk  is  heated  and  evapo- 
rated in  partial  vacuum.  The  origin 
of  the  term  "pan"  has  not  been 
satisfactorily  explained.  In  the  early 
and  experimental  days  of  the  manu- 
facture of  condensed  milk,  the  milk 
was  evaporated  in  open  kettles, 
called  pans.  It  is  probable  that  the 
name  of  this  primitive  apparatus 
was  passed  on  to  the  more  perfected 
machinery  now  in  use. 

The  vacuum  pans  are  construct- 
ed of  copper,  iron,  steel  or  bronze 
Practically  all  of  the  vacuum  pans 
used  for  condensing  milk  are  made 
of  copper  throughout ;  they  are  of 
various  styles  and  sizes.  The  pre- 
dominating size  used  in  milk  con- 

denseries  is  the  "six-foot  pan."  By  the  term  six-foot  is  meant  a 

retort  measuring  six  feet  in  diameter. 

There  are  two  general  types  of  vacuum  pans  on  the  market ; 
pans  that  are  relatively  wide  in  diameter  and  shallow  in  depth, 
and  pans  of  relatively  narrow  diameter  and  which  have  a  deep 
body.  Both  types  are  claimed,  by  their  respective  manufacturers, 
to  have  special  advantages,  such  as  ease  of  operation,  uniformity 
of  action,  economy  of  fuel  and  of  water,  and  rapidity  of  evapora- 


15. 


Vacuum  pan   and  condenser 
Courtesy   of   Groen   Mfg.    Co. 


SWEETENED  CONDENSED  MILK — CONDENSING 


69 


tion  ;  the  opinions  of  the  users  of  these  pans  are  also  at  variance 
concerning  their  relative  merits. 

The  advocates  of  the  wide,  shallow  pan  claim  that  this  type 


Fig-.   16 
Vacuum  pan   and  condenser 

Courtesy  of 
Arthur  Harris  &  Co. 


Fig*.  16-A.     Covering*  and  insulation  for 
vacuum  pans 

Courtesy  of  Arthur  Harris  &  Co. 


70 


CONDENSED  MILK — CONDENSING 


of  pan  makes  possible  such  an  arrangement  of  the  heating  sur- 
face as  to  take  care  of  the  maximum  amount  of  milk  with  the 
minimum  depth  of  milk  over  the  heating  surface  and  that  this 
arrangement  is  most  desirable.  They  hold  that  because  the  wide 
and  shallow  pan  offers  a  larger  area  of  evaporating  surface,  it 
therefore  makes  possible  more  rapid  evaporation  than  the  narrow, 
deep  pan.  They  further  emphasize  that  in  the  wide,  shallow 
pan,  the  milk  boils  more  quietly,  is  under  better  control  and  is 
less  apt  to  be  carried  over  into  the  condenser  and  lost,  than  in 
the  narrow,  deep  pan. 

The  advocates  of  the 
narrow,  deep  pan  claim  that 
their  type  of  pan  increases 
the  rapidity  of  evaporation 
because  it  causes  the  milk 
to  pass  over  the  heating  sur- 
face more  rapidly.  When 
the  pan  is  in  operation,  the 
boiling  milk  travels  from  the 
center  of  the  bottom  toward 
the  periphery  where  it  rises, 
rolls  over  the  coils,  and  re- 
turns to  the  center.  It  is 
claimed  that  a  pan  with  a 
shallow  jacket,  such  as  the 
rtarrow,  deep  pans  have, 
causes  the  milk  to  roll  over 
higher,  especially  if  the  coils 
are  close  to  the  periphery 
and  leave  plenty  of  vacant 
space  in  the  center  of  the 
pan.  This,  in  turn,  means 
more  rapid  circulation  of  the 
milk,  causing  it  to  pass  over  the  heating  surface  at  greater  speed, 
and  oftener,  which  naturally  enables  the  milk  to  utilize  more  heat 
and,  therefore,  to  evaporate  more  quickly.  Because  in  such  pans 
the  milk  rolls  over  higher,  they  require  a  deeper  body. 

Experience  has  demonstrated  .that  for  maximum  rapidity  of 
evaporation,  other  factors  being  the  same,  maximum  rapidity  of 


Fig.    17.      Vacuum  pan   and   condense! 

Courtesy  of  Mojonnier  Bros.   Co. 


SWEETENED  CONDENSED  MILK — CONDENSING 


71 


circulation  of  the  milk  over  the  heating  surface  is  indispensable. 
It  is  further  obvious  that  the  rapidity  of  evaporation  is  in  direct 
relation  to  the  area  of  the  heating-  surface. 

Rapidity  of  circulation  of  the  milk  demands  that  there  be 
no  hindering  counter  currents  and  that  the  milk  be  permitted 
to  circulate  with  maximum  freedom  in  one  direction.  This  can 
best  be  accomplished  by  leaving  a  large  open  space  in  the  center 
for  the  milk  to  return  to  the  bottom  after  it  has  boiled  up  and 
over  the  coils  from  the  periphery. 

In  order  to  have  the  coils  so  ar- 
ranged as  to  permit  this  maximum  and 
unhindered  circulation  of  the  milk,  the- 
pan  must  have  a  certain  height  or 
depth,  so  as  to  admit  the  necessary 
heating  surface. 

With  the  growing  recognition  of 
these  principles,  vacuum  pan  manufac- 
turers are  therefore  more  and  more 
tending  toward  the  style  of  pan  with  a 
tall  body  in  proportion  to  its  diameter. 
The  vacuum  pan  consists  of  four 
main  parts,  namely,  the  jacket  or  bot- 
tom, the  body  or  vapor  belt,  the  dome 
and  the  condenser. 

The  Jacket  forms  the  bottom  of 
the  pan.  The  inside  wall  is  copper,  the 
outside  cast  iron.  It  generally  is  con- 
cave, the  curve  varying  in  different 
types  of  pans  from  a  depth  of  a  few 
inches  to  two  and  one-half  feet.  The 
steam  space  in  the  jacket  between 
inner  and  outer  walls  is  about  two 
inches  wiide.  It  is  equipped  with  two 
steam  inlets  and  one  or  two  steam 
outlets.  In  some  pans  some  or  all  of 
the  steam  outlets  of  the  coils  also  ex- 
haust through  the  jacket. 
In  the  center  of  the  bottom  there  is  an  opening,  from  two 
to  three  inches  in  diameter,  for  the  discharge  of  the  condensed 


Piff.   18 
Vacuum   pan   and  condenser 

Courtesy   of  C.   E.   Rogers 


72  SWEETENED  CONDENSED  MILK — CONDENSING 

milk,  fitted  with  a  valve.  In  the  case  of  pans  that  have  no 
special  "striking"  or  sampling  cup,  this  discharge  is  equipped 
with  two  valves  and  a  short  nipple  between  valves,  to  make 
possible  the  sampling  of  the  condensed  milk  while  the  pan  is  in 
operation. 

The  Body  or  Vapor  Belt  represents  the  main  part  of  the 
pan.  It  is  cylindrical,  of  varying  height  and  is  equipped  with 
copper  coils  wrhich  have  their  outlets  either  through  the  jacket 
or  the  walls  of  the  body.  Their  upper  ends  connect,  through 
t'he  body  of  the  pan,  with  the  main  steam  line.  Most  pans  are 
equipped  with  two  to  three  or  more  coils  located  at  different 
elevations.  Since  steam  should  be  turned  into  the  coils  only  when 
they  are  covered  with  the  milk,  it  is  desirable  to  have  several 
short  independent  coils  rather  than  but  one  large  one.  This 
will  give  a  larger  range  of  the  quantity  of  milk  that  can  be  con- 
densed and  increases  the  speed  of  evaporation.  The  coils  vary 
in  diameter  from  about  three  to  six  inches.  The  upper  and  outer 
coils  are  the  larger  ones.  The  diameter  and  length  of  the  coils 
necessarily  vary  with  and  are  limited  by  the  capacity  of  the  pan. 
The  shorter  each  individual  coil,  and  the  greater  the  number  of 
independent  coil  sections  and  the  greater  the  total  heating  sur- 
face, consistent  with  maximum  rapidity  of  circulation  of  the 
milk  and  with  easy  access  to  all  parts  of  the  jacket  and  coijs, 
the  better.  Other  things  being  equal,  the  more  square  feet  of 
heating  surface,  the  less  steam  pressure,  by  the  gauge,  is  required 
to  furnish  the  necessary  heat  for  maximum  evaporation.  This 
is  important  because  high  steam  pressure  in  the  jacket  and  coils 
means  exposure  of  the  milk  to  high  temperature,  which  is  un- 
desirable. .  The  heating  surface  should  be  sufficient  to  make, 
possible  the  complete  condensation  of  the  steam  in  the  jacket 
and  coils.  If  the  heating  surface  is  inadequate,  more  steam  has 
to  be  turned  into  the  jacket  and  coils,  in  order  to  secure  the 
necessary  heat  for  rapid  evaporation,  than  will  condense;  free 
steam  will  blow  through  and  out  of  the  coils,  resulting  in  un- 
economic and  wasteful  use  of  fuel,  and  jeopardizing  the  quality 
of  the  product.  The  presence  of  numerous  but  short  coils  also 
increases  the  intensity  of  heat-transmission,  as  practically  all 
of  the  steam  is  condensed  in  the  uppermost  convolution  of  each  coil. 
There  is  a  considerable  variation  in  the  area  of  the  heating  sur- 


SWEETENED  CONDENSED  MILK — CONDENSING 


Tig.  19.     Steam  coils  in  Harris  pan 

Courtesy  of  Arthur  Harris  &  Co. 


face  in  different  makes  of  pans,  ranging  from  about  120  to  205 
square  feet,  in  the  case  of  six  foot  pans.  • 

In  the  latest  improvement 
in  coils  each  independent  coil 
makes  only  one  turn  in  the  pan 
and  the  inner  and  outer  coils 
have  the  same  inlet  and  dis- 
charge and  are  placed  on  the 
same  level.  This  permits  of 
the  installation  of  a  larger 
number  of  independent  coils, 
each  placed  at  a  different  level. 
In  this  manner  the  coils  can  be 
utilized  to  better  advantage. 
This  is  especially  significant 
when  the  volume  of  milk  in  the 
pan  is  very  small,  making  pos- 
sible the  operation  of  the  lower  coils  independent  of  the  upper 
coils  and  thereby  avoiding  the  danger  of  burning  the  milk,  which 
inevitably  occurs  when  the  heated  coils  are  not  completely  sub- 
merged. This  arrangement  increases  the  heating  efficiency  of 
the  pan,  heat  can  be  turned  on  the  lowest  coil  almost  immediately 
after  starting  operation,  and  toward  the  end  of  the  batch,  when 
the  milk  again  boils  low,  some  of  the  coils  are  still  covered  and 
can  be  used.  The  shorter  length  of  these  coils  from  inlet  to 
exhaust  also  makes  possible  the  simultaneous  utilization  of  a 
greater  volume  of  steam.  These  combined  features  materially 
increase  the  rapidity  of  evaporation  and  augment  the  capacity 
of  the  pan.  These  improved  coils  have  the  further  advantage 
that  their  exhausts  do  not  have  tx>  be  carried  through  the  jacket, 
but  pass  through  the  body  of  the  pan. 

Jacket  and  coils  are  connected  independently  with  the  direct 
steam  main  from  the  boiler.  Each  connection  at  the  pan  should 
carry  a  valve  and  a  steam  gauge  on  the  pan-side  of  the  valve. 
The  main  steam  line  and  connections  leading  to  pan  should  be 
properly  insulated  by  proper  pipe  coverings,  in  order  to  supply 
the  pan  with  as  dry  steam  as  possible. 

The  drips  or  discharge  ends  of  the  jacket  and  coils  are  con- 
nected with  the  boiler  feed  water  tank.  If  the  pan  has  sufficient 


74  SWEETE)N£D  CONDENSED  MILK — CONDENSING 

heating  surface  and  is  operated  properly,  the  drip  ends  of  the 
jacket  and  coils  should  discharge  warm  water  only,  and  not  free 
steam.  The  jacket  and  coils  should  be  free  at  the  drip  or  dis- 
charge ends  so  that  all  condensation  water  may  be  quickly  and 
continuously  removed.  This  is  necessary  in  order  to  make  the 
most  economical  use  of  the  steam  and  to  secure  high  efficiency 
of  evaporation.  In  order  to  guard  against  back  pressure  the 
drips  may  be  equipped  with  suitable  check  valves. 


Fig*.  20.     Steam  coils  in  Rogers  pan 

Courtesy  of  C.  E.  Rogers 

Through  the  walls  of  the  body  of  the  pan  also  enters  the 
milk  draw  pipe.  This  pipe  connects  with  the  hot  well  and  through 
it  the  milk  rushes  into  the  pan.  Immediately  outside  of  the 
pan  the  milk  pipe  should  be  equipped  with  a  valve  to  regulate 
the  inflow.  The  size  of  the  milk  draw  pipe  and  valve  is  governed 
by  the  capacity  of  the  pan ;  usually  two  to  three  inches  in  di- 
ameter. Inside  of  the  pan  the  milk  pipe  should  be  turned  down. 
If  this  provision  is  not  made,  the  milk  shoots  straight  across  the 


SWEETENED  CONDENSED  MILK— CONDENSING 


75 


pan  atomizing-  into  a  dense  spray,  which  is  partly  drawn  over 
into  the  condenser,  causing  loss  of  milk. 

The  body  of  the  pan  also  usually  carries,  near  its  lower 
portion,  a  sampling  cup,  or  striking  cup,  which  facilitates  the 
sampling  and  testing  for  density,  of  the  contents  of  the  pan 
while  the  pan  is  in  operation. 

A  suitable,  permanent  covering  should  be  provided  for  the 
body  of  the  pan  for  insulation  against  heat  radiation.  This  will 
not  only  economize  fuel  and  speed  evaporation,  but  it  will  also 

assist  in  keeping  the  pan  room 

reasonably  cool. 

The  Dome  rests  on  top  of 
the  body  of  the  pan.  It  is  equip- 
ped with  a  manhole,  manhole 
cover,  thermometer,  vacuum 
gauge,  sight  glasses,  lights, 
blow-down  valve  or 
vacuum  breaker.  The 
manhole  measures 
about  fourteen  to 


Fig.    21.      Vacuum   gauge 

Courtesy   of   Arthur   Harris   &  Co. 


eighteen  inches  in  di- 


ameter.    It    is    closed 
by  a  solid  brass  cover 

with  a  well-fitting,  ground  surface  flange.  The  cover 
carries  a  five-inch  spy-glass  or  sight-glass  through 
which  the  operator  watches  the  boiling  milk  in  the 
pan.  The  stem  of  the  thermometer  is  enclosed  in  a 
brass  casing  and  reaches  to  near  the  bottom  of  the 
pan.  Some  processors  prefer  a  short  thermometer 
which  registers  the  temperature  of  the  vapors  instead 
of  that  of  the  milk.  As  both,  the  milk  and  the  vapors 
are  subjected  to  the  same  pressure,  their  respective 
temperatures  are  the  same.  The  vacuum  gauge  con- 
nects with  the  interior  of  the  pan,  and  indicates  the 
number  of  inches  of  vacuum.  A  mercury  column  may 
be  used  in  the  place  of  the  vacuum  gauge.  In  the 
rear  of  the  dome  there  are  two  sight  glasses.  Through 

.  .  •  f     ,  ••«•••  j   t.  •     Courtesy    of 

these  the  interior  of  the  pan  is  illuminated  by  means  c.  E.  Rogers 


Fig.  22 

Mercury 
Column 


76  SWEETENED  CONDENSED  MILK  —  CONDENSING 

of  lamps,  gas   or   electric   lights.     The  "blow-down"   valve,   or 

vacuum  breaker,   serves  to  admit  air  into  the  pan  in  order  to 

"break"  the  vacuum.    This  is  necessary  for  readily 

drawing  off   the   finished   condensed   milk.     It   is 

further  needed  to  prevent  the  contents  of  the  vacu- 

um pan  from  being  drawn  over  into  the  condenser, 

whenever  the  milk  rises  above  a  safe  level. 

A  further  accessory  of  the  dome  may  be  an 
automaotic  milk  sampler.  The  sampler  tube  is 
carried  through  the  wall  of  the  dome  and  extends 
to  near  the  bottom  inside  of  the  pan.  Where  this 
t  .il:e  projects  through  the  dome  it  is  equipped  with 
motor,  piston  pump,  striking  cup  and  hydrometer.' 
The  striking  cup  at  its  upper  end  terminates  in  a 
small  chamber  equipped  with  a  sight-glass  through 

which  the  operator  notes  the  position  of  the  hydro- 

Thermometer 

meter.  for  vacuum  pan 


The      Condenser. 
-The     condenser     is  &c°- 

that  portion  of  the  condensing  ap- 
paratus in  which  the  vapors,  rising 
from  the  boiling  milk  in  the  pan,  are 
condensed  to  water.  The  condenser 
is  attached  to  the  dome  of  the  pan. 
There  are  three  types  of  condensers 
in  use,  the  surface  condenser,  the 
barometric  condenser  and  the  wet- 
vacuum  spray  condenser. 

The  Surface  Condenser  consists 
of  a  tube  cylinder  filled  with  brass 
tubes,  mounted  on  a  receiver.  The 
water  used  for  cooling  circulates  out- 
side of  the  tubes  and  the  vapors  pass 
Fig..  24.  through  the  tubes,  where  they  are 

Vacuum  breaker  or  blow-down  chilled     and    condensed.       This    COn- 

Courtesy  Arthf/Harris  &  Co.       denser  has  the  advantage  of  enabling 

the  operator  to  note  the  amount  of 

condensation  and  to  measure  the  amount  of  water  actually  con- 
densed.    The  receiver  at  the  bottom  of  the  condenser  should  be 


SWEETENED  CONDENSED  MILK — CONDENSING 


77 


so  arranged  that  it  can  be  drained  at  will  and  without  interfering 
with  or  retarding  the  operation  of  the  pan. 

The  Barometric  Condenser  consists  of  a  vertical  cylinder  of 
iron  or  brass,  equipped  with  a  spray  jet,  through  which  the  cool- 


Fig-.  25.    Vacuum  pan  with  dry  vacuum  barometric  condenser 

Courtesy  of  Arthur  Harris  &  Co. 

ing  water  enters  the  condenser.  The  vapors  being  drawn  over 
from  the  violently  boiling  milk  in  the  pan,  are  condensed  by 
passing  through  this  spray  of  cold  water.  This  condenser  dis- 
charges its  water  into  a  tight  cistern  in  the  ground.  The  con- 
denser is  placed  so  that  its  bottom  flange  is  about  thirty-five 


78  SWEETENED  CONDENSED  MILK — CONDENSING 

feet  above  the  water  level  of  the  cistern  in  which  the  discharge 
pipe  from  the  condenser  terminates.  The  height  of  the  condenser 
depends  on  the  barometric  pressure  of  the  location  where  it  is 
installed.  The  lower  the  altitude  and,  therefore,  the  higher  the 
atmospheric  pressure,  the  higher  must  the  condenser  be  above 
the  cistern.  At  the  sea  level,  the  atmospheric  pressure  sustains 
a  water  column  about  thirty-four  feet  high.  This  water  column 
in  the  discharge  pipe  seals  the  vacuum  and  at  the  same  time 
permits  the  water  from  the  spray  and  the  condensation  water 
to  escape  automatically.  The  cistern  in  which  the  water  column 
terminates  should  be  of  sufficient  size  to  hold  about  one-third 
more  water  than  the  capacity  of  the  entire  length  of  the  discharge 
pipe  calls  for  and  should  have  a  large  overflow  into  the  sewer. 
When  the  pan  is  in  operation  and  a  uniform  vacuum  is  main- 
tained, the  level  of  the  water  column  remains  constant  and  the 
excess  water  from  the  condenser  overflows  from  the  cistern  into 
the  sewer. 

The  Wet-Vacuum  Spray 
Condenser  consists  of  a  huge 
hollow  cylinder  of  brass  or  iron, 
usually,  but  not  necessarily, 
horizontal. 

The  horizontal  spray  con- 
densers are  usually  equipped  pi^  26-  wet-vacuum  horizontal 

ri^  spray  condenser 

with  a  perforated  spray  pipe,  Courtesy  of  Arthur  Harris  &  Co. 
placed  lengthwise  in  the  cyl- 
inder. This  spray  pipe  should  run  close  to  the  top  side  of  the 
cylinder,  so  as  to  give  the  spray  that  escapes  from  the  holes  on 
the  upper  side  of  the  spray  pipe  a  chance  to  strike  the  top  of  the 
horizontal  cylinder  with  force  and  to  become  atomized.  The 
spray  pipe  connects  at  the  end  nearest  the  pan  with  the  pipe 
supplying  the  cooling  water.  When  the  pan  is  in  operation, 
a  shower  of  cold  water  issues  forth  from  the  perforations  of  the 
spray  pipe  as  the  result  of  the  reduced  pressure  in  pan  and  con- 
denser. The  force  with  which  the  water  escapes  these  perfora- 
tions is  further  augmented  by  the  fact  that  in  most  cases  the 
water  supply  tank  is  located  higher  than  the  condenser.  The 
hot  vapors  arising  from  the  boiling  milk  in  the  pan  are  drawn 
over  into  the  condenser,  where  they  come  in  contact  with  the 


SWEETENED  CONDENSED  MILK — CONDENSING  79 

cold  water  spray  and  are  condensed.  The  bottom  of  the  con- 
denser cylinder,  at  the  end  farthest  from  the  pan  is  connected 
with  the  suction  end  of  the  vacuum  pump  through  which  the 
water  and  the  condensed  vapors  in  the  condenser  escape.  Man- 
holes with  covers  should  be  provided  at  the  top  and  end  of  the 
condenser  cylinder  to  facilitate  the  cleaning"  out  of  the  condenser. 
In  the  vertical  spray  condenser  the  condenser  cylinder  is 
upright,  located  either  on  top  of  the  pan  or  at  some  distance,  as 
is  the  case,  for  instance,  where  a  catch-all  is  installed  between 


Fig*.   27.     Diagonal  spray  condenser 
Courtesy  of  Mojonnier  Bros.  Co. 

pan  and  condenser.  The  interior  arrangement  of  the  vertical 
condenser  varies  somewhat  with  the  different  makes.  One  type 
of  vertical  condenser  widely  used  in  American  condenseries  con- 
sists of  a  double  insulated  vapor  tube  resting  on  top  of  the  pan. 
This  insulated  tube  is  surrounded  by  and  connects  with  a  spray 
chamber,  which  terminates  at  its  top  in  a  perforated  metal  plate, 
and  \vhich  has  an  opening  in  the  side  near  the  bottom  that  con- 
nects with  the  vacuum  pump  supplying  the  suction  and  that 
permits  the  escape  of  the  condensed  vapors  and  cooling  water. 
The  cooling  water  enters  at  the  top  of  the  condenser.  Immediately 
underneath  the  wrater  inlet  it  strikes  a  metal  cone  or  umbrella 
which  prevents  the  water  from  running  into  the  vapor  tube,  and 


80 


•SWEETENED  CONDENSED  MILK — CONDENSING 


distributes  it  evenly  over  the  perforated  spray  plate.  The  vapor 
rises  into  the  vapor  tube  of  the  condenser  and  is  drawn  over 
into  the  spray  chamber  surrounding"  it,  where  the  vapor  is  con- 
densed by  the  spray  of  water  issuing  from  the  perforated  spray 
plate  which  tops  the  spray  chamber  and  which  contains  a  large 
number  of  very  small  holes.  As  the  water  falls  through  these 
openings  by  gravity,  the  spray  is  uniform  and  constant  and  does 


Tig.  28.     Vertical  spray  condenser 

Courtesy  of  C.  E.  Rogers 

not  depend  on  the  amount  of  water  used,  nor  does  it  require 
water  pressure  on  the  condenser.  A  complete  sheet  of  spray  al- 
ways is  formed,,  through  which  the  vapors  must  pass,  regardless 
of  the  amount  of  water  used,  a  fact  which  assists  in  the  efficient 
use  of  the  water  and  in  rapid  and  complete  condensation  of  the 
vapors.  Manholes  with  covers  are  located  at  the  top  to  facili- 
tate the  cleaning  of  the  spray  plate. 


SWEETENED  CONDENSED  MILK — CONDENSING  81 

In  another  type  of  vertical  spray  condenser  the  insulated 
vapor  tube  in  the  center  is  surrounded  by  a  spray  chamber  of 
much  greater  width,  and  the  water  spray  starts  near  the  bottom 
of  the  chamber  from  perforations  in  a  circular  coil.  The  per- 
forations are  so  located  that  the  spray  slants  upward  and  out- 
ward. As  it  strikes  the  periphery  of  the  condenser,  it  is  deflected 
downward  and  toward  the  center.  It  is  claimed  that  in  this 
case  two  sheets  of  spray  are  formed,  through  which  the  vapors 
must  pass.  Baffle  plates  extend  downward  and  outward  from  the 
top  of  the  vapor  tube  preventing  any  of  the  spray  from  entering 
the  vapor  tube.  Manholes  with  covers  are  provided  at  the  sides 
to  make  possible  easy  cleaning  of  the  condenser. 

Instead  of  the  condenser  being;  attached  direct  to  the  dome 
of  the  vacuum  pan,  the  condenser  may  form  a  part  of  the  vacuum 
pump.  This  arrangement  is  feasible  both  in  the  case  of  the  wet- 
vacuum  spray  condenser  and  in  the  case  of  the  surface  condenser. 

The  chief  difference  between  the  wet-vacuum  condenser  and 
the  barometric  condenser  is  that  in  the  wet-vacuum  condenser 
the  water  from  the  condenser  passes  through  the  vacuum  pump, 
while  in  the  barometric  condenser  the  water  does  not  pass 
through  the  vacuum  pump,  but  goes  direct  into  the  sewer  and  the 
vacuum  is  sealed  by  the  barometric  water  column.  So  far  as 
practical  experience  has  shown,  there  is  no  material  difference 
in  the  efficiency  between  these  two  types  of  condensers.  The 
water  column  of  the  barometric  condenser  helps  somewhat  to 
maintain  a  uniform  vacuum.  It  necessitates,  however,  the  in- 
stallation of  the  pan  inconveniently  high  and  requires  somewhat 
more  expensive  machinery  than  is  the  case  with  the  wetfvacuum 
condenser.  The  chief  difference  between  both  of  these  systems 
and  the  surface  qondenser  is  that,  in  the  wet-vacuum  and  baro- 
metric condensers  the  condensed  vapors  mix  with  the  cooling 
water,  while  in  the  surface  condenser  the  condensed  vapors  are 
collected  and  carried  off  separately  and  without  mixing  with 
the  cooling-  water.  In  the  case  of  condensing  liquids,  the  vapors 
of  which  are  of  commercial  value,  the  surface  condenser  must  be 
used.  The  surface  condenser,  however,  is  of  relatively  small 
capacity  and  the  cooling  water  cannot  be  utilized  as  economically 
as  in  the  case  of  the  other  systems.  Where  large  quantities  of 
vapors  are  to  be  handled  and  the  vapors  have  no  commercial 


82 


SWEETENED  CONDENSED  MILK — CONDENSING 


value,  as  is  the  case  in  condensing-  milk,  the  barometric  and  wet- 
vacuum  condensers  are  best  suited ;  if  properly  constructed,  their 
operation  utilizes  the  cooling1  water  most  economically. 

Care  of  the  Condenser. — In  the  operation  of  the  spray  and 
jet  condenser,  special  attention  should  be  paid  to  the  condition 
of  the  spray  pipe,  or  spray  plate.  Especially,  when  the  water 
used  contains  much  organic  matter,  as  is  the  case  with  water 
from  a  creek,  pond  or  lake,  there  is  a  tendency  of  the  spray  equip- 
ment becoming  filled  and  coated  with  slimy  organic  matter, 
causing  the  perforations  to  clog.  This  renders  the  distribution 
of  the  spray  irregular  and  the  control  of  the  pan  difficult.  It 
causes  great  waste  of  water  because  much  of  the  water  is  dis- 
charged from  the  condenser  and  lost  without  coming  into  direct 
contact  with  the  vapors.  The  water  is,  therefore,  not  utilized 
economically  and  the  difference  between  the  temperature  of  the 
vapors  and  the  discharge  of  the  condenser  is  excessive.  In  order 
to  avoid  this  the  condenser  should  be  cleaned  out  thoroughly  at 
least  once  a  week,  or  oftener  if  necessary,  to  keep  the  pores  of 
the  spray  pipe  or  plate  free  from  obstructions.  It  is  advisable  to 
install  condensers  equipped  with  a  manhole,  properly  located, 
otherwise  access  to  the  spraying  arrangement  is  not  sufficiently 
convenient  to  insure  frequent  inspection  and  thorough  cleaning 
by  the  average  operator. 

The  Expansion  Tank,  Catch-All,  or  Milk  Trap.— This  is  a 
tank  frequently  installed  between 
the  dome  of  the  pan  and  the  con- 
denser. Its  purpose  is  to  collect  and 
reclaim 'any  milk  that  may  be  carried 
over  from  the  pan  and  to  prevent 
its  escape  and  loss  through  the  con- 
denser. 

If  the  pipe  through  w;hich  the 
milk  enters  the  pan  is  turned  down 
and  its  end  is  carried  to  near  the 
bottom  of  the  pan,  so  as  to  avoid 
the  formation  of  excessive  milk 
spray,  if  the  pan  is  operated  care- 
fully and  if  the  milk  is  kept  at  a  ***•  29-  vacuum  pan  with  milk 
reasonably  low  level,  there  is  very  courtesy  of  Arthur  Harris  &  Co. 


SWEETENED  CONDENSED  MILK — CONDENSING  83 

little  danger  of  milk  being  carried  over  into  the  condenser  in 
quantities  sufficient  to  be  of  any  consequence.  Under  these 
conditions  the  installation  of  a  special  milk  trap  between  the 
pan  and  the  condenser  for  the  purpose  of  collecting  the  escaping 
milk  spray  and  carrying  it  back  to  the  pan  is,  therefore,  an 
unnecessary  expense. 

If  the  pan  is  small  in  comparison  to  the  amount  of  milk  to 
be  condensed,  and  if  it  is  forced  beyond  its  intended  capacity  so 
that  the  milk  boils  up  high,  there  usually  is  considerable  loss  of 
milk,  as  indicated  by  the  foaminess  and  milky  color  of  the  ex- 
haust of  the  vacuum  pump.  In  such  cases  the  mechanical  loss' 
of  an  average  size  batch  may  amount  to  several  hundred  pounds 
of  milk.  In  order  to  not  lose  this  milk,  a  milk  trap  or  catch-all 
may  be  installed  between  the  pan  and  the  condenser.  The  vapors 
laden  with  the  milk  spray  enter  the  trap  near  the  top.  The 
spray  drops  to  the  bottom  of  the  trap,  while  the  vapors  are  drawn 
over  into  the  condenser,  where  they  are  condensed  as  usual. 
This  trap  may  be  constructed  of  sufficient  size  so  as  to  serve 
as  a  reservoir  to  collect  all  the  milk  that  is  carried  over,  and  at 
the  conclusion  of  the  process  the  contents  of  the  trap  are  drawn 
from  the  bottom  and  are  condensed  with  the  .next  batch ;  or  the 
bottom  of  the  trap  may  be  connected  with  the  pan  so  that  the 
milk  thus  carried  over  flows  back  into  the  pan  automatically. 
In  this  case  a  small  trap  only  is  necessary. 

It  should  be  understood  that  the  milk  trap  is  only  a  remedy 
and  not  a  preventive.  Where  the  capacity  of  the  pan  is  in  pro- 
portion to  the  amount  of  milk  to  be  condensed,  as  it  should  be, 
and  where  the  pan  is  operated  properly,  the  trap  is  unnecessary. 
The  trap  is  an  additional  piece  of  apparatus  to  be  kept  clean. 
Unless  it  is  so  constructed  that  access  can  be  had  t'o  all  parts 
of  its  interior  and  unless  it 
really  is  kept  clean  at  all  times, 
it  may  become  a  serious  source 
of  contamination. 

The  Vacuum  Pump.— The 
vacuum  pump  is,  strictly  speak- 
ing, not  a  part  of  the  vacuum 
pan,  but  its  intimate  connec- 

1  .  Figf.   30.      Wet-vacuum  pump 

tion      With      the      pan      makes      it          CourteSy  of  Arthur  Harris  &  Co. 


84  SWEETENED  CONDENSED  MILK — CONDENSING 

necessary  to  briefly  consider  it  at  this  point.  The  suction  end 
of  the  vacuum  pump  is  connected  with  the  condenser.  The 
vacuum  pump  exhausts  the  pan,  forming  a  partial  vacuum. 
There  are  principally  two  types  of  vacuum  pumps  used  in 
the  milk  condensery,  the  dry-vacuum  pump  and  the  wet- 
vacuum  pump.  The  dry-vacuum  pump  is  used  in  the  factories 
with  the  dry-vacuum  system,  i.  e.,  where  the  cooling  water 
and  the  condensation  water  escape  to  the  sewer  direct 
and  without  passing  through  the  vacuum  pump,  as  is  the  case 
with  the  surface  condenser  and  the  barometric  condenser.  The 
wet-vacuum  pumps  are  used  with  the  wet-vacuum  system,  where 
the  cooling  water  and  the  condensation  water  pass  through  the 
cylinder  of  the  pump.  The  dry-vacuum  pumps  have  the  advan- 
tage of  permitting  the  operation  of  the  machine  at  a  higher 
piston  speed  than  the  wet-vacuum  pumps  in  which  the  water 
must  be  displaced  at  the  end  of  each  stroke.  The  cylinders  of 
the  dry-vacuum  pump  are  cooled  by  water  jackets.  The  initial 
cost  of  the  dry-vacuum  pumps,  however,  is  greater  than  that 
of  the  wet-vacuum  pumps. 

The  efficiency  of  the  vacuum  apparatus  depends  very  largely 
on  the  vacuum  pump.  Rapid  evaporation  at  a  relatively  low 
temperature  necessitates  the  maintenance  of  a  high  vacuum.  The 
type,  material,  construction,  workmanship,  installation  and  oper- 
ation of  the  vacuum  pump  should  be  such  as  to  insure  the  maxi- 
mum efficiency. 

The  pump  should  be  placed  on  a  good  foundation  and  as 
near  the  vacuum  pan  as  practicable  in  order  that  the  full  benefit 
of  the  vacuum  may  be  realized.  The  suction  pipe  and  all  con- 
nections must  be  tight.  The  suction  pipe  must  be  of  the  size 
directed  by  the  manufacturer,  as  short  as  possible  and  with  few 
and  easy  bends.  The  grade  of  the  suction  pipe  should  be  uni- 
form in  order  to  avoid  air  pockets. 

The  water  should  be  turned  into  the  condenser  before  the 
vacuum  pump  is  started.  The  pump  should  not  run  at  a  higher 
speed  than  is  necessary  to  secure  the  required  vacuum.  Exces- 
sive speed  means  high  steam  consumption  and  heavy  wear  and 
tear  on  the  pump.  The  amount  of  water  supplied  to  the  con- 
denser should  be  regulated  to  suit  the  requirements.  Ordinarily, 
and  with  a  vacuum  of  twenty-five  to  twenty-six  inches,  the 


SWEETENED  CONDENSED  MILK — CONDENSING  85 

temperature  of  the  condenser  discharge  should  be  about  110  de- 
grees F.  A  lower  temperature  would  cause  excessive  and  un- 
economic use  of  water  unless  the  available  water  has  a  temper- 
ature lower  than  is  the  case  in  the  average  American  condensery 
(50  to  60°  F.).  The  basin  on  the  vacuum  cylinder  should  be 
kept  filled  with  water  to  prevent  admission  of  air  to  the  cylinder 
through  the  stuffing  box,  and  the  spray  pipe,  jet,  or  spray  plate  in 
the  condenser  should  be  inspected  often  to  make  sure  that  the 
perforations  are  not  clogged.  The  stuffing  box  of  the  cylinder 
should  be  well  packed  with  a  good  quality  of  packing  and  the 
steam  cylinde-r  well  oiled.  Start  the  pump  slowly.  Belt-driven 


Tig.   31.     Wet-vacuum  pump 

Courtesy  of  Union  Steam  Pump  Co. 

pumps,  especially  those  equipped  with  a  fly-wheel,  insure  greater 
uniformity  of  speed  than  direct-acting,  steam-driven  pumps. 
Steam-driven  pumps  should  be  furnished  with  a  high  grade  gov- 
ernor. The  vacuum  pump  should  have  a  capacity  proportionate 
to  the  size  of  the  vacuum  pan,  amount  of  heating  surface,  steam 
pressure  and  temperature  of  condensing  water. 

Science  and  Practice  of  Evaporating  in  Vacuo. 

Purpose  of  Condensing  in  Vacuo. — The  important  advan- 
tages gained  by  evaporating  milk  under  reduced  pressure,  or  in 
vacuo,  are :  economy  of  evaporation,  rapidity  of  evaporation,  low 
temperature  and  large  capacity  of  apparatus.  All  of  these  features 
are  essential  in  the  successful  condensing  of  milk. 


86  SWEETENED  CONDENSED  MILK — CONDENSING 

Rapid  evaporation  cannot  take  place  until  the  milk  is  brought 
to  the  boiling  point  and  is  kept  there  until  evaporation  is  com- 
pleted. Under  atmospheric  pressure  and  at  the  sea  level,  the 
boiling  point  of  water  is  212  degrees  F.,  the  boiling  point  of  milk 
is  very  slightly  higher,  about  214  degrees  F.  Evaporation  of  milk 
under  atmospheric  pressure  in  an  open  kettle,  however,  is  a 
relatively  slow  process,  requiring  a  long  time  and  large  appara- 
tus. Furthermore,  exposure  of  the  milk  to  212  to  214  degrees 
F.  long  enough  to  complete  evaporation  would  render  the  prod- 
uct unsuitable  for  market.  The  properties  of  some  of  its  ingre- 
dients are  altered,  the  product  would  assume  a  dark  color  and 
a  marked  cooked  flavor  as  the  result  of  the  effect  of  heat.  All 
of  these  objections  are  minimized  and  partly  avoided  by  lower- 
ing the  boiling  point  of  milk.  These  objections,  however,  do 
not  apply  to  evaporation  under  atmospheric  pressure  by  film 
treatment,  as  is  the  case  with  the  Continuous  Concentrator  de- 
scribed in  Chapter  XIV. 

•    Relation  of  Pressure  to  Boiling  Point. — The  temperature  at 
which  milk  boils  depends  on  the  pressure  to  which  it  is  exposed. 


SWEETENED  CONDENSED  MILK — CONDENSING 


87 


The  table  below  shows  the  boiling-  point  of  water  at  pres- 
sures ranging  from  atmospheric  pressure  at  the  sea  level  (14.72 
pounds  per  square  inch)  to  a  complete  vacuum. 


Boiling   Points   of   Water  at   Different   Vacua.1 


Absolute  pres- 
sure per 
square  inch 

Vacuum  inches 
of  mercury 
column 

Vacuum  milli- 
meters 
of  mercury 
column 

Temperatures 
of    boiling 
point    of 
water,  F. 

Temperatures 
of    boiling 
point    of 
water,  C. 

14.720 

0.00 

00 

212.00 

100.00 

14.010 

1.42 

36 

209.55 

98.5 

13.015 

3.45 

88 

205.87 

96.8 

12.015 

5.49 

139 

201.96 

94.3 

11.020 

7.52 

191 

197.75 

91.9 

10.020 

9.56 

243 

193.22 

89.5 

9.020 

11.60 

295 

188.27 

86.75 

8.024 

13.63 

346 

182.86 

83.7 

7.024 

15.67 

398 

176.85 

80.5 

6.024 

17.70 

450 

170.06 

76.8 

5.029 

19.74 

502 

162.28 

72.5 

4.029 

21.78 

553 

153.01 

67.2 

3.034 

23.81 

605 

141.52 

60.8 

2.034 

25.85 

657 

126.15 

52.3 

1.040 

27.88 

708 

101.83 

38.7 

.980 

28.00 

712 

.100.00 

37.8 

.735 

28.50 

724 

90.00 

32.2 

.544 

28.89 

734 

80.00 

26.7 

.402 

29.18 

741 

70.00 

21.1 

.294 

29.40 

747 

60.00 

15.6 

.216 

29.56 

751 

50.00 

10.0 

.162 

29.67 

754 

40.00 

4.4 

.127 

29.74 

756 

32.00 

By  courtesy  of  the  Buffalo  Foundry  &  Machine  Company. 


88  SWEETENED  CONDENSED  MILK — CONDENSING 

The  pressure  or,  correctly  speaking,  the  vacuum,  is  expres- 
sed in  terms  of  inches  of  mercury  which  the  atmospheric  pressure 
sustains.  The  mercury  column  is  not  a  direct  measure  of  the 
pressure,  but  it  shows  the  difference  between  the  atmospheric 
pressure. and  the  absolute  pressure  in  the  vacuum  chamber.  The 
atmospheric  pressure  at  the  sea  level  is  14.7  pounds  per  square 
inch.  It  sustains  a  mercury  column  in  an  absolute  vacuum  of 
30  inches  at  62  degrees  F.3  and  of  29.922  inches  at -32  degrees  F. 
The  absolute  vacuum  may  be  calculated  by  multiplying  the 
atmospheric  pressure  by  the  factor  2.04.  In  case  there  is  only 
a  partial  vacuum  the  mercury  column  sustained  is  lowered  to  the 
extent  of  the  absolute  pressure  in  the  vacuum  pan.  The  absolute 
pressure  may  be  calculated  as  follows : 

Example:  The  actual  vacuum  in  the  pan  is  25  inches  at  the 
sea  level.  What  is  the  absolute  pressure? 

14  7  \/  (30 25) 

— ^—          — —  2.45  pounds  of  absolute  pressure  per  sq.  inch. 

Ov_/ 

Relation  of  Altitude  to  Atmospheric  Pressure. — At  altitudes 
higher  than  the  sea  level,  the  atmospheric  pressure  is  reduced 
and  the  mercury  column  is  lowered.,  though  the  absolute  pres- 
sure in  the  vacuum  pan  may  be  the  same.  Therefore,  in  factories 
located  at  high  altitudes  the  mercury  column  will  show  fewer 
inches  of  vacuum  at  a  given  temperature  and  with  a  given 
absolute  pressure.  • 

The  following  table  shows  0the  barometric  reading  in  inches 
of  mercury  column  and  the  atmospheric  pressure  in  pounds  per 
square  inch  at  different  altitudes : 


SWEETENED  CONDENSED  MILK — CONDENSING 


89 


Barometric  Reading  Corresponding  with  Different  Altitudes.1 


Barometric 
reading  in 
inches  of 
mercury 

Atmospheric 
pressure  in 
pounds  per 
square  inch 

Altitude 
above  sea 
level  in  feet 

Barometric 
reading  in 
inches  of 
mercury 

Atmospheric 
pressure  in 
pounds  per 
square  inch 

Altitude 
above  sea 
level 
in  feet 

30.0 

14.72 

0 

23.5 

11.54 

6412 

29.7 

14.60 

264 

23.0 

11.30 

6977 

29.5 

14.47 

441    . 

22.5 

11.05 

7554 

29.2 

14.35 

710 

22.0 

10.80 

8144 

29^0 

14.23 

890 

21.5 

10.56 

8747 

28.7 

14.11 

1163 

21.0 

10.31 

9366 

28.5 

13.98 

1347 

20.0 

9.81 

10648 

28.2 

13.86 

1625 

19.0 

9.32 

11994 

28.0 

13.74 

1812 

18.0 

8.82 

13413 

27.5 

13.50 

2285 

17.0 

8.33 

14914 

27.0 

13.26 

2767 

16.0 

7.84 

16506 

26.5 

13.02 

3257 

15.0 

7.35 

18201 

26.0 

12.77 

3758 

14.0 

6.86 

19996 

25.5 

12.53 

4268 

13.0 

6.37 

21891 

25.0 

12.27 

4787 

12.0 

5.88 

.23886 

24.5 

12.03 

5318 

11.0 

5.39 

25981 

24.0 

11.78 

5859 

By  courtesy  of  the  Buffalo  Foundry  &  Machine  Company. 


90 


SWEETENED  CONDENSED  MILK — CONDENSING 


In  the  following-  table  may  be  found  the  altitudes  of  various 
cities  in  the  United  States : 

Altitude  in  Feet  of  Various  Cities  in  the  United  States. 
By  Courtesy  of  United  States  Department  of  Agriculture. 


Akron,  Ohio   940 

Albany,  N.  Y 22 

Atlanta,  Ga 1032 

Baltimore,  Md 92 

Birmingham,  Ala 600 

Boston,   Mass 16 

Buffalo,  N.  Y 583 

Burlington,  Vt 112 

Butte,  Mont 5555 

Charleston,  S.  C 12 

Chattanooga,  Tenn 672 

Chester,  Pa.    22 

Chicago,  111 590 

Cincinnati,   Ohio    490 

Cleveland,  Ohio 582 

Dayton,  Ohio   740 

Denver,  Colo 5183 

Dallas,  Tex 430 

Des  Moines,  Iowa 805 

Detroit,   Mich •  588 

Duluth,  Minn 609 

Houston,  Tex 46 

Indianapolis,   Ind 708 

Ithaca,  N.  Y 411 

Kansas  City,  Mo 750 

Knoxville,  Tenn 890 

Lexington,  Ky 955 

Little  Rock,  Ark.  264 


Los  Angeles,  Cal 267 

Louisville,  Tenn 453 

Memphis,  Tenn 256 

Milwaukee,  Wis 593 

Minneapolis,  Minn. 812 

New  Haven,  Conn.   10 

New  Orleans,  La 6 

New  York  City 54 

Oklahoma  City,  Okla 1197 

Omaha,  Neb.  * ..1016 

Philadelphia,  Pa 42 

Phoenix,  Ariz. 1082 

Pittsburgh,  Pa 743 

Providence,  R.  1 11 

Richmond,  Va 51 

Rochester,  N.  Y 510 

St.  Louis,  Mo 455 

Salt  Lake  City,  Utah  .  . .  .4238 

San  Francisco,  Cal 15 

Santa  Fe,  N.  M.   .'. 6952 

Seattle,  Wash 10 

South  Bend,  Ind 717 

Spokane,  Wash 1908 

Tampa,  Fla.    . 15 

Washington,  D.  C 25 

Wichita,   Kan 1294 

Vicksburg,  Miss 196 


SWEETENED  CONDENSED  MILK  —  CONDENSING  91 

According  to  Kent1  the  relation  of  altitude  to  atmospheric 
pressure  per  square  inch  is  as  follows: 

Pounds  Pressure 
Altitude  Per  Square  Inch 

At    sea    level  ...................................  14.7 

£  mile  above  sea  level  ..........  .  ...............  14.02 

J  mile  above  sea  level  ..........................  13.33 

f  mile  above  sea  level  ..........................  12.66 

1  mile  above  sea  level  ..........................  12.02 

1^  miles  above  sea  level  ...........  .  ...........  ..  .11.42 

1^  miles  above  sea  level  .........................  10.88 

2  miles  above  sea  level  ...............  ..........  9.80 

"For  a  rough  approximation  we  may  assume  that  the  pres- 
sure decreases  one-half  pound  per  square  inch  for  every  -1,000 
feet  of  ascent." 

The  absolute  pressure  in  the  pan  of  a  factory  located  at 
Omaha,  Neb.,  with  an  altitude  of  1,016  feet  above  sea  level,  and 
condensing  in  an  actual  vacuum  of  twenty-five  inches,  would 
then  be  as  follows  : 

Atmospheric  pressure  =  14.7  —  .5  =  14.2  pounds  per  square 
inch. 

Absolute  vacuum  =   14.2  X2.04  =  28.97  inches. 

14  ?  v  (?8  97  __  i  25) 
Absolute  pressure  =  —    -  -  "n>7       —  —  —   1.95  pounds 


per  square  inch. 

Relation  of  Steam  Pressure  in  Jacket  and  Coils,  Water  in 
Condenser,  Temperature  in  Pan  and  Vacuum,  to  Rapidity  of 
Evaporation.  —  The  temperature  of  the  vapors  in  the  vacuum  pan 
depends  directly  upon  the  pressure  or  vacuum  under  which  they 
are  generated.  The  more  nearly  complete  the  vacuum  and,  there- 
fore, the  lower  the  pressure,  the  lower  is  the  temperature,  and, 
other  conditions  being  the  same,  the  more  rapid  the  evaporation. 
The  pressure  in  turn  is  governed  by  the  capacity  of  the  vacuum 
pump,  the  tightness  of  the  joints,  the  steam  pressure  in  jacket 
and  coils  and  the  amount  and  temperature  of  the  water  in  the 
condenser. 

1  Mechanical  Engineer's  Pocket-Book,  p.  581. 


92  SWEETENED  CONDENSED  MILK — CONDENSING 

With  a  low  capacity  vacuum  pump,  or  a  pump  running 
irregularly,  or  too  slow,  or  too  fast,  and  with  leaky  joints,  the 
vacuum  will  always  be  low,  and  the  pressure  and  temperature 
relatively  high.  Under  these  conditions  the  pan  is  difficult  to 
operate  and  evaporation, is  slow. 

With  the  above  conditions  under  control  and  properly  adjus- 
ted and  with  a  given  area  of  heating  surface  and  arrangements  of 
it  for  proper  circulation  of  the  milk,  the  temperature  and  the 
rapidity  of  evaporation  depend  on  the  steam  pressure  in  the 
jacket  and  coils  and  on  the  amount  and  temperature  of  the  water 
used  in  the  condenser. 

Twenty-five  pounds  of  steam  pressure  in  the  jacket  and  coils 
has  been  found  to  be  about  the  maximum  that  can  safely  be  used. 
With  this  steam  pressure  the  milk  coming  in  direct  contact  with 
the  heating  surface  is  exposed  to  about  267  degrees  F.  and  there 
is  a  tendency  for  some  of  it  to  bake  or  burn  on,  which  is  unde- 
sirable. The  walls  of  the  jacket  and  coils  are  also*  subjected  to 
considerable  strain,  since  they  are  surrounded  by  an  almost  com- 
plete vacuum.  Then  ag~ain,  if  the  pan  has  the  proper  amount 
of  .heating  surface  the  capacity  of  the  condenser  and  the  water 
supply  are  in  most  cases  insufficient  to  take  care  of  and  condense 
the  vapors  arising  from  the  boiling  milk  in  the  pan,  when  the 
steam  pressure  in  jacket  and  coils  approaches  or  exceeds  twenty- 
five  pounds.  Most  condenseries  operate  their  pans  with  five  to 
fifteen  pounds  of  steam  pressure  in  jacket  and  coils.  In  the  oper- 
ation of  some  pans  not  more  than  about  five  pounds  steam  pres- 
sure can  be  used  economically  in  jacket  and  coils,  because  the  use 
of  more  steam  causes  the  steam  to  blow  through  and  out  of  the 
coils. 

Aside  from  the  principle  of  construction  the  capacity  of  the 
condenser  used  in  milk  condenseries  is  very  largely  dependent  on 
the  water  supply.  W7he'never  the  condenser  is  forced  beyond  its 
capacity,  by  using  excessive  steam  in  jacket  and  coils,  the  vacuum 
drops,  the  temperature  rises  and  the  process  of  evaporation  is 
retarded. 

The  higher  the  vacuum  the  more  rapid  the  evaporation.  A 
rise  in  the  steam  pressure  in  the  jacket  and  coils  increases  the 


CONDENSED  MILK — CONDENSING  93 

rapidity  of  evaporation  only  as  long  as  enough  water  passes 
through  the  condenser  to  maintain  a  high  vacuum.  As  soon  as 
the  steam  pressure  in  the  jacket  and  coils  reaches  the  point  where 
the  water  in  the  condenser  fails  to.  promptly  reduce  the  vapors/ 
the  vacuum  drops,  the  temperature  in  the  pan  rises  and  evapora- 
tion is  checked. 

The  condensing  of  milk  requires  immense  quantities  of  water ; 
experience  has  shown  that  it  takes  from  one  to  three  gallons  of 
water  to  condense  one  pound  of  fresh  milk,  the  exact  amount 
depending  on  the  construction  of  the  condenser  and  the  tempera- 
ture of  the  water.  The  water  supply  is  one  of  the  weakest  links 
in  most  condenseries,  so  that  economy  of  water  is  one 
of  the  important  factors  to  be  considered.  The  steam  pressure 
in  the  jacket  and  coils  should,  therefore,  be  so  regulated  as  to 
make  it  possible  to  maintain  the  maximum  vacuum  consistent 
with  reasonably  economic  use  of  water.  With  a  vacuum  of 
twenty-five  inches  the  temperature  in  the  pan  is  about  135  de- 
grees F.,  the  temperature  varying  somewhat  with  the  altitude 
of  the  factory.  In  some  condenseries  the  temperature  of  the  pan 
is  kept  at  150  degrees  F.  This  practice  may  economize  the  water 
a  trifle  better,  but  the  rapidity  of  evaporation  is  considerably 
lower. 

Condensing  at  temperatures  lower  than  130  degrees  F.,  with- 
out reducing  the  steam  pressure  in  the  jacket  and  coils,  increases 
the  rapidity  of  evaporation,  but  taxes  the  water  supply  beyond 
the  reach  of  most  condenseries.  vSo  much  water  has  to  be  used 
in  the  condenser  that  it  is  not  used  economically,  as  is  showrn  by 
the  relatively  low  temperature  of  the  water  discharging  from  the 
condenser.  The  temperature  of  the  condenser  discharge  bears 
a  direct  relation  to.  the  temperature  of  the  vapors  in  the  pan. 
Observations  made  in  various  factories  and  under  different  con- 
ditions by  Hunziker  and  others  sho\ved  that  the  condenser  dis- 
charge was  anywhere  from  5  to  25  degrees  F.  lower  in  tempera- 
ture than  the  vapors  in  the  pan.  the  difference  averaging  about 
15  degrees  F. 

The  smaller  the  difference  in  temperature  between  the  con- 
denser discharge  and  the  vapors  in  the  pan,  the  more  economic 
is  the  use  of  the  water  and  vice  versa.  It  is  not  advisable  under 


94  SWEETENED  CONDENSED  MILK — CONDENSING 

average  conditions  to  so  operate  the  pan  that  the  temperature 
of  the  condenser  discharge  drops  below  110  degrees  F.,  because 
of  the  wasteful  use  of  water  under  such  conditions. 

The  condensing  of  one  pound  of  milk  requires  about  one 
pound  of  steam  and  ten  to  twenty-five  pounds  of  water.  The 
number  of  heat  units  used  for  condensing  in  vacuum  is  practically 
the  same  as  that  required  by  evaporating  in  open  pans.  In  order 
to  use  the  steam  economically  the  pan  should  be  so  operated  as 
to  make  possible  its  complete  condensation  by  the  time  it  leaves 
the  jacket  and  coils,  Whenever  so  much  steam  is  used  that  it 
blows  through  and  out  of  the  jacket  and  coils  without  being  con- 
densed, there  is  great  waste  of  fuel.  For  further  details  on  this 
point  see  "Description  of  the  Vacuum  Pan." 

Starting  the  Pan. — Before  drawing  the  milk  into  the  pan,  the 
pan  should  be  thoroughly  rinsed  with  water,  then  steamed  until 
the  temperature  rises  to  about  180  degrees  F.  or  above.  Then 
the  manhole  cover  is  put  in  place,  all  the  air  valves  are  closed, 
water  is  turned  into  the  condenser  and  the  vacuum  pump  is 
started.  When  the  vacuum  gauge  shows  over  twenty  inches  of 
vacuum,  the  pan  is  ready  for  the  milk. 

Operating  the  Pan. — The  valve  of  the  milk  pipe  leading  to 
the  pan  is  now  partly  opened.  The  milk  enters  the  pan  auto- 
matically as  the  result  of  the  reduced  pressure  in  the  pan.  When 
the  milk  covers  the  jacket,  steam  is  gradually  turned  into  the 
jacket.  As  each  coil  becomes  submerged  in  milk,  the  coils  are 
charged  with  steam.  At  no  time  should  steam  be  turned  on  the 
jacket  and  coils  when  they  are  not  completely  covered  with  milk, 
as  such  action  would  cause  the  milk  to  stick  to  and  burn  on  the 
heating  surface,  the  milk  would  assume  a  burnt  flavor,  it  would 
become  permeated  with  black  specks  and  the  evaporation  would 
be  retarded.  On  the  start,  but  a  few  pounds  of  steam  pressure 
should  be  used  in  the  jacket  and  coils,  to  avoid  burning,  owing 
to  the  presence  in  the  milk  of  considerable  air.  As  the  milk 
becomes  more  concentrated  and  settles  down  to  uniform  boiling, 
the  steam  pressure  may  be  gradually  increased  until  it  reaches 
the  maximum.  The  maximum  pressure  permissible  must  be  gov- 
erned by  the  amount  of  heating  surface,  the  capacity  of  the  vacu- 
um pump  and  the  temperature  and  amount  of  water  available  for 


SWEETENED  CONDENSED  MILK — CONDENSING  95 

use  in  the  condenser.     Under  average  conditions  about  fifteen 
pounds  of  steam  pressure  may  be  safely  used. 

During  the  early  stages  of  the  pro-cess,  when  the  milk  is  of 
low  density,  the  evaporative  duty  is  high,  probably  about  twenty- 
five  to  thirty-five  pounds  per  square  foot  of  heating  surface  with 
ten  pounds  of  steam  pressure.  This  gradually  decreases  and  is 
lowest  toward  the  end  of  the  process. 

When  enough  milk  is  in  the  pan  to  completely  cover  the 
jacket  and  coils,  the  milk  intake  should  be  reduced  and  regulated 
in  accordance  with  the  rate  of  evaporation.-  The  milk  is  drawn 
into  the  pan  continuously,  but  only  as  fast  as  it  evaporates.  It 
should  be  kept  as  much  as  possible  at  a  constant  level,  and  this 
level  is  preferably  as  low  as  is  consistent  with  complete  covering 
of  the  upper  most  coil. 

In  order  to  secure  maximum  rapidity  of  evaporation,  the 
vacuum  pump  should  run  at  the  proper  speed  and  its  operation 
should  be  uniform,  a  uniform  vacuum  and  temperature  should 
be  maintained  and  the  milk  should  be  prevented  from  rising  to 
an  abnormally  high  level  in  the  pan. 

-  Prevention  of  Accidents. — The  operator  should  pay  strict 
attention  to  the  pan  in  order  to  avoid  loss  of  milk  due  to  acci- 
dents. He  should  watch  the  water  supply  and  govern  its  use 
accordingly.  If  the  water  supply  becomes  exhausted,  air  is  liable 
to  be  drawn  into  the  pan  through  the  condenser.  This  will  cause 
the  milk  to  drop  suddenly  and  then  rise  in  a  body,  threatening 
to  escape  through  the  condenser.  Whenever  air  in  considerable 
quantities  is  allowed  to  enter  the  pan  while  in  operation,  be  it 
as  the  result  of  lack  of  water,  or  through  any  other  cause,  or 
when  the  vacuum  pump  is  allowed  to  stop  and  live  steam  is 
turned  into  the  milk  in  the  pan,  as  is  the  case  when  the  milk 
is  superheated,  the  escape  of  milk  may  be  avoided  by  immediately 
shutting  the  steam  inlet  to  the  jacket  and  coils,  by  closing  the 
milk  intake  and  by  slightly  opening  the  blow-down  valve  when- 
ever the  milk  rises  dangerously  high.  By  skillful  manipulation 
of  the  blow-down  valve  until  the  milk  again  settles  down  to 
uniform  boiling,  loss  can  be  avoided  and  the  process  can  be  con- 
tinued in  the  normal  way. 


96  SWEETENED  CONDENSED  MII.K — STRIKING 

By  the  time  all  the  milk  is  in  the  pan,  condensation  is  nearly 
completed,  and  from  ten  to  twenty  minutes  further  boiling  usu- 
ally gives  the  milk  the  desired  density.  Toward  the  end  of  the 
.process  the  steam  pressure  in  jacket  and  coils  should  be  reduced 
to  about  five  pounds  or  less.  When  the  milk  approaches  the 
desired  density,  it  is  comparatively  heavy  and  viscous  and  boils 
less  vigorously.  It  therefore  is  more  directly  exposed  to  the 
heating  surface.  In  the  case  of  excessive  steam  pressure,  its 
quality  is  jeopardized.  If  the  batch  is  small  so  that  the  level 
of  the  milk  drops  below  some  of  the  coils,  steam  to  the  exposed 
coils  should  be  turned  off  entirelv. 


CHAPTER  VI. 

STRIKING  OR  FINISHING  THE  BATCH. 

Definition. — When  the  boiling  milk  in  the  vacuum  pan  ap- 
proaches the  desired  degree  of  concentration,  the  batch  is 
"struck."  The  term  "striking"  is  applied  to  the  operation  of 
sampling  the  condensed  milk  and  testing  the  sample  for  density. 
This  term  very  probably  referred,  originally,  to  the  meaning  of 
"striking  the  batch  right,"  that  is,  stopping  the  process  at  the 
proper  time,  or  when  the  milk  is  neither  too  thick  nor  too  thin. 
It  then  expressed  the  result  of  the  operation,  while  now  it  is 
used  to  mean  the  operation  itself. 

Ratio  of  Concentration. — Sweetened  condensed  milk  intended 
for  canned  goods  has  a  specific  gravity  of  1.28  to  1.30.  This 
density  is  reached  usually  when  the  ratio  of  concentration  is 
about  2.5:1,  i.  e.,  2.5  parts  of  fresh  milk  are  condensed  to  one 
part  of  condensed  milk,  assuming  that  about  sixteen  pounds  of 
sucrose  have  been  added  to  every  one  hundred  pounds  of  fresh 
milk. 

Occasionally  the  ratio  of  concentration  is  based  qn  the  pro- 
portion of  water  evaporated,  in  which  case  it  is  obviously  much 
higher  than  when  based  011  the  amount  of  milk  required  to  make 
one  pound  of  condensed  milk,  because  the  added  cane  sugar 
takes  the  place  of  its  own  weight  of  water,  and  thereby  acts  as* 
a  diluent  of  the  condensed  milk.  Thus  let  us  assume  that  16 


CONDENSED  MIUC — STRIKING  97 

pounds  of  cane  sugar  are  added  to  every  100  pounds  of  fresh 
milk  and  that  it  takes  250  pounds  of  fresh  milk  to  make  100 
pounds  of  sweetened  condensed  milk,  100  pounds  of  sweetened 
condensed  milk,  therefore,  contain  16  ><  2.5  —  40  pounds  of  cane 
sugar.  Using  the  sugar-free  finished  product  as  the  basis  for 
calculation,  then,  the  ratio  of  concentration  would  be : 

250 

-=:4.17  to  1. 


(100  —  40) 

Instead  of  giving  the  ratio  of  concentration,  this  basis  of 
calculation  determines  the  ratio  of  evaporation  only.  The  results 
are,  therefore,  erroneous  and  misleading.  It  does  not  materially 
matter  whether  the  diluent  in  the  condensed  milk  is  water  or 
cane  sugar,  or  both ;  the  really  important  factor  is  the  per  cent 
milk  solids  in  the  condensed  milk  as  compared  with  the  per  cent 
solids  in  the  original  fresh  milk,  and  this  relation  is  solely  deter- 
mined by  the  amount  of  fluid  milk  required  to  make  one  pound 
of  condensed  milk,  or  by  the  true  and  actual  ratio  of  concentra- 
tion. If  it  takes  2\  pounds  of  fresh  milk  for  every  pound  of  con- 
densed milk,  then  the  ratio  of  concentration  is  obviously  2.5  to 
1  and  not  4.17  to  1. 

Methods. — To  know  just  when  the  proper  degree  of  concen- 
tration has  been  reached  is  difficult  and  requires  experience.  It 
is  here  where  the  processor  can  easily  make  or  lose  his  wages. 
There  are  various  indications  reminding  the  observant  processor 
that  the  milk  in  the  retort  is  nearly  ''done,*'  viz.,  time  consumed 
for  condensing,  time  elapsed  since  all  the  milk  has  been  "drawn 
up/'  amount  of  condensed  milk  left  in  the  pan  and;  most  of  all, 
the  appearance  and  behavior  of  the  boiling  mirk  itself.  Milk 
that  has  been  sufficiently  condensed  assumes  a  glossy,  glistening 
lustre,  it  boils  over  from  the  periphery  towards  the  center,  form- 
ing a  small  nucleus  or  puddle  of  foam  in  the  center  of  the  pan. 
An  experienced  and  observant  operator  knows  within  a  few  min- 
utes when  the  milk  is  condensed  enough.  This  does  not  mean, 
however,  that  he  should  wait  until  the  last  minute  before  he 
"strikes"  the  batch,  for  even  the  most  skillful  and  experienced 


98  SWEETENED  CONDENSED  MILK — STRIKING 

processors  are  easily  deceived  by  the  mere  appearance  of  the  con- 
densed milk  through   the  sight  glass. 

The  degree  of  concentration  may  be  more  accurately  deter- 
mined by  taking  a  sample  from  the  pan  and  testing  it  by  various 
methods,  such  as  by  weighing  a  definite  quantity  of  condensed 
milk  on  a  sensitive  scale,  by  the  use  of  a  resistance  apparatus, 
or  viscosimeter,  or  by  the  use  of  a  specially  constructed  hydrom- 
eter. Of  these  the  Beaume  hydrometer  has  been  found  the 
most  suitable  to  use  under  average  factory  conditions. 

Mechanical  devices  and  instruments,  such  as  above  enumer- 
ated can  be  depended  upon,  when  all  conditions  influencing  the 
specific  gravity  of  the  product,  such  as  chemical  composition 
and  temperature,  are  under  control.  Their  successful  use  ren- 
ders careful  and  accurate  standardization  of  the  milk  for  butter- 
fat,  solids  not  fat,  and  sucrose  indispensable.  Without  standardi- 
zation of  the  component  ingredients  of  milk  the  result  of  the 
use  of  these  devices  may  prove  erroneous  and  misleading. 

The  operation  of  these  devices  must  also  be  simple  and  rapid, 
for  when  the  boiling  and  rapidly  evaporating  milk  in  the  pan 
approaches  the  proper  density,  quick  action  is  essential.  One 
minute  over  or  under  condensing  may  cause  the  milk  to  be 
either  too  thick  or  too  thin  for  the  market,  and  may  necessitate 
the  "rerunning"  of  the  entire  batch. 

In  the  absence  of  a  satisfactory  instrument  for  rapid  deter- 
mination of  the  concentration,  and  particularly  in  the  absence  of 
a  carefully  standardized  product,  the  experienced  eye  and  the 
good  judgment  of  the  processor  are  all  essential.  The  following 
factory  methods  have  been  found  applicable  and  reasonably 
reliable. 

Determination  by  Appearance  to  the  Eye. — Draw  a  sample 
from  the  pan  into  a  tin  dipper,  lower  the  dipper  into  a  pail  of 
ice  water  or  snow.  Stir  the  condensed  milk  with  a  metal-back 
thermometer  until  the  condensed  milk  is  cooled  to  70  degrees  F. 
Note  the  thickness  of  it.  Or,  finish  the  batch  at  a  constant  tem- 
perature, say  120  degrees  F.  Draw  a  sample  into  a  tin  cup  and 
note  the  thickness  by  examining  the  milk  when  pouring  from 


SWEETENED  CONDENSED  MILK — STRIKING 


99 


Tig.  32. 
Beaum6  hy- 
drometer for 
sweetened 
condensed 

milk 

Courtesy 

C.  J.  Tagliabue 

Mfg-.  Co. 


a  teaspoon.  The  transparency  of  the  milk  when  thus 
held  against  the  light  and  the  manner  in  which  the 
milk  piles  up  in  the  cup  furnish  a  practical  index  to 
its  density.  The  last  method  is  preferable  because 
of  its  greater  rapidity.  For  best  results  the  use  of 
a  Beaume  hydrometer,  especially  constructed  for 
sweetened  condensed  milk,  graduated  to  from  30 
to  37  degrees  B.  and  with  subdivisions  of  one-tenth 
degrees  is  recommended. 

Use  of  Beaume  Hydrometer. — Beginners  and 
inexperienced  operators  do  well  to  take  numerous 
samples  from  the  batch  in  the  operating  pan  and  to 
start  sampling  early,  so  as  to  avoid  over-condens- 
ing. No  definite  figure  at  which  the  Beaume  hydrom- 
eter should  be  read  can  be  stated  that  would  show 
the  proper  density  under  all  conditions.  The  Beaume 
reading  of  sweetened  condensed  milk  of  the  proper 
concentration  varies  with  such  factors  as  per  cent 
of  fat,  per  cent  of  sucrose  and  per  cent  solids,  ratio 
of  concentration  and  temperature  of  the  condensed 
milk  when  the  reading  is  taken.  However,  for  gen- 
eral guidance,  it  may  be  stated  that  condensed  milk 
of  a  concentration  of  2.5  :  1,  made  from  fresh  milk 
of  average  richness  and  containing  sucrose  at  the 
ratio  of  sixteen  pounds  of  sugar  per  one  hundred 
pounds  of  fresh  milk,  will  show  a  Beaume  reading 
of  about  33.5  degrees  B.  at  60  degrees  F.,  or  about 
32  degrees  B.  at  120  degrees  F.  Sweetened  con- 
densed skim  milk  containing  approximately  40  per 
cent  sucrose  will  showr  a  Beaume  reading  at  60  de- 
grees F.  of  about  37  degrees  B.,  or  about  35.5  de- 
grees B.  at  120  degrees  F.  If  it  is  intended  to  use 
more  sugar  (44%)  and  to  limit  the  per  cent  milk 
solids  to  28  per  cent,  whole  milk  is  condensed  until 
the  Beaume  hydrometer  at  130  degrees  F.  shows 
3H  degrees  B.  Skimmed  sweetened  condensed  milk 
containing  28  per  cent  milk  solids  and  42  per  cent 
sucrose  tests  about  34}  degrees  B.  at  130  degrees  F. 


100  SWEETENED  CONDENSED  Miuc — STRIKING 

Correction  of  Hydrometer  Reading  for  Temperature. — The 
Beaume  hydrometers  used  in  American  condenseries  are  grad- 
uated to  give  correct  readings  at  60  degrees  F.  If  the  readings 
are  to  be  correct,  or  if  it  is  desirable  to  convert  them  into  spe- 
cific gravity,  the  condensed  milk  should  have  a  temperature  of 
60  degrees  F.  Where  this  is  not  convenient,  the  observation  may 
be  made  at  any  temperature  convenient  and  the  reading  corrected 
as  follows : 

When  the  temperature  is  above  60  degrees  F.  multiply  the 
difference  between  the  observed  temperature  and  60  degrees  F. 
by  the  factor  .025  and  add  the  product  to  the  observed  reading  of 
the  Beaume  hydrometer.  When  the  temperature  of  the  observed 
reading  is  below  60  degrees  F.  the  corresponding  product  is 
deducted. 

Examiple:  Beaume  reading  at  120  degrees  F.  is  31.2.  Cor- 
rected reading  is  31.2  +  [.025  X  (120  —  60)]  =  327. 

The  specific  gravity  may  be  calculated  when  the  Beaume 
reading  is  known,  by  using  the  following  formula : 

1443 

Specific  gravity  =   1  . .  „   — 5—;  B.  —  Beaume  reading. 
144.0  —  Jj . 

Example:    Beaume  reading,  at  60  degrees  F.  is  33.1. 

144  3 
Specific  grvity  =  :   1443_331       =  1.2976    _ 

In  the  following  table  are  assembled  figures  showing  the  spe- 
cific gravity  of  sweetened  condensed  milk  of  different  Beaume 
degrees,  varying  from  28  degrees  B.  to  37.8  degrees  B. 


SWEETENED  CONDENSED  MILK — STRIKING 


101 


Specific  Gravity  of  Sweetened  Condensed  Milk  of  Different 
Beaume  Degrees. 


Beaume1  at 
60  degrees  F. 

Specific 
Gravity 

Beaum6  at 
60  degrees  F. 

Specific 
Gravity 

28.0 

1.2407 

33.0 

1.2965 

.2 

1.2428 

.2 

1.2988 

.4 

1.2449 

.4 

1.3011 

.6 

1.2471 

.6 

1.3034 

.8 

1.2493 

.8 

1.3058 

29.0 

1.2515 

34.0 

1.3082 

.2 

1.2536 

.2 

1.3106 

.4 

1.2558 

.4 

1.3130 

.6 

1.2580 

.6 

1.3154 

.8 

1.2602 

.8 

1.3178 

30.0 

1.2624 

35.0 

1.3202 

2 

1.2646 

2 

1.3226 

.4 

1.2668 

.4 

1.3250 

.6 

1.2690 

.6 

1.3274 

.8 

1.2713 

.8 

1.3299 

31.0 

1.2736 

36.0 

1.3324 

.2 

1.2758 

2 

1.3348 

.4 

1.2780 

.4 

1.3372 

.6 

1.2803 

.6 

1.3397 

.8 

1.2826 

.8 

1.3422 

32.0 

1.2849 

37.0 

1.3447 

.2 

1.2872 

2 

1.3472 

.4 

1.2895 

.4 

1.3497 

.6 

1.2918 

.6 

1.3522 

.8 

1.2941 

.8 

1.3548 

102 


CONDENSED  MILK — STRIKING 


Sampling  of  Batch. — The  samples  can  be  drawn  from  the 
pan  by  operating  the  two  valves  at  the  bottom  explained  under 
"Description  of  Vacuum  Pan."  While  the  milk  is  condensing, 
the  partial  vacuum  in  the  pan  makes  impossible  the  drawing  off 
of  the  sample  by  simply  opening  the  outlet.  Instead  of  causing 
the  milk  to  come  out,  air  would  rush  in  writh  violent  force  and 
would  cause  the  milk  in  the  pan  to  be  thrown  over  into  the  con- 


Fig*.  33.    A  con- 
venient device 
for  sampling- 
tile  condensed 

milk  in  the  pan 

Courtesy  of 

Arthur  Harris 

&  Co. 


Fig*.  34.     A  convenient  device  for  sampling1 

condensed  milk  in  the  pan 
Courtesy  of  Arthur  Harris  &  Co. 


denser,  besides  dangerously  jolting  the  machinery.  For  this  rea- 
son the  outlet  is  equipped  with  two  valves,  both  of  which  are 
closed  during  the  condensing  process.  For  taking  samples,  open 
the  upper  valve.  This  allows  the  condensed  milk  to  run  into 
the  nipple  between  the  two  valves.  Now  close  the  upper  valve 
and  open  the  lower  one.  The  milk  will  run  out  freely.  The  first 
sample  should  be  rejected,  as  it  may  contain  water  caught  in 
the  nipple. 

For  greater  convenience  and  increased  rapidity  of  sampling, 
especially  constructed  sample  cups  or  striking  cups,  attached  to 
the  side  of  the  body  of  the  pan  may  be  used.  These  striking  cups 


SWEETENED  CONDENSED  MILK — COOLING  103 

are  now  made  of  such  size  that  the  hydrometer  can  be  operated 
in  them,  rendering  the  use  of  a  separate  hydrometer  cylinder 
unnecessary.  The  latest  invention  for  facilitating  the  sampling 
and  striking  is  the  automatic  milk  striker  designed  by  Mojonnier 
Bros.  Co.,  Chicago.  This  ingenious- contrivance  consists  of  a 
motor-driven  piston  pump.  The  suction  tube  carrying  the  piston 
extends  from  the  dome  of  the  pan  into  the  boiling  milk.  This 
tube  projects  at  its  upper  end  through  the  wall  of  the  dome  and 
overflows  into  a  hydrometer  cylinder.  This  cylinder  carries  at 
its  upper  end  a  chamber  permitting  unhindered  motion  of  the 
hydrometer  and  the  end  of  this  chamber  which  faces  the  operator 
is  equipped  with  a  sight  glass  and  a  light.  In  the  cylinder 
reposes  a  Beaume  hydrometer.  Whenever  the  operator  desires 
to  know  the  density  of  the  condensed  milk  in  the  pan,  he  starts 
the  motor.  The  pump  immediately  fills  the  cylinder  and  the 
hydrometer  shows  the  density  or  Beaume  reading. 

Drawing  off  the  Condensed  Milk, — As  soon  as  the  evapora- 
tion is  completed,  the  steam  is  shut  off  from  the  jacket  and  coils, 
the  water  valve  is  closed,  the  vacuum  pump  stopped  and  the 
vacuum  broken  by  opening  the  "blow-down"  valve.  The  man- 
hole cover  is  then  removed  and  the  vacuum  pump  started  again 
in  order  to>  remove  the  hot  air  over  the  milk.  The  milk  is  drawn 
into  40-quart  cans  or  into  tanks  or  cooling  vats.  The  condensed 
milk  should  be  drawn  from  the  pan  as  rapidly  as  possible  to 
prevent  its  superheating  while  in  the  pan.  In  some  factories  a 
wire  mesh  or  cloth  strainer  is  attached  to  the  outlet  of  the  pan, 
so  that  the  condensed  milk  is  strained  before  it  runs  into  the 
cans  This  practice  is  unnecessary  and  objectionable,  as  it  tends 
to  retard  the  removal  of  the  milk  from  the  pan. 

COOLING. 

The  sweetened  condensed  milk,  as  it  comes  from- the  vacuum 
pan,  has  a  temperature  of  about  115°  F.  to  130°  F.  If  it  were 
allowed  to  cool  naturally,  or  on  its  own  accord,  i.  e.,  if  no  effort 
were  made  to  cool  it  promptly,  it  would  superheat  and  this  would 
cause  it  to  become  thick  and  cheesy  in  a  short  time.  It  is,  there- 
fore, essential  that  it  be  cooled  at  once.  Formerly  this  was  done 
by  drawing  the  milk  from  the  pan  into  40  quart  cans,  setting 
these  filled  cans  in  tanks  with  ice  water  and  stirring  the  con- 
densed milk  with  a  stick, 


104  SW£E;TE;NE;D  CONDENSED  Miuc — COOUNG 

This  was  a  very  crude  method,  it  involved  much  hard  work 
and  time,  and  the  quality  of  the  product  was  poor.  It  was  soon 
found  that  the  imperfect  hand  stirring  caused  excessive  sugar 
crystallization,  which  made  the  milk  sandy.  The  sudden  chilling 
and  irregular  stirring  of  a  saturated  sugar  solution  like  sweet- 
ened condensed  milk  are  favorable  to  the  formation  of  sugar 
crystals.  Where  the  stirring  is  imperfect  and  irregular,  all  the 
milk  is  not  kept  in  sufficient  motion  to  insure  uniform  and  gradual 
cooling.  The  milk  next  to  the  side  of  the  cans  is  chilled  too 
abruptly,  favoring  the  formation  of  crystals.  Vigorous  stirring 
in  itself  is  conducive  of  sugar  crystallization. 

Later  the  hand  stirring  was  completely  superseded  by 
mechanical  stirring,  paddles  closely  scraping  the  sides  of  the 
cans  being  used.  Instead  of  setting  the  paddles  in  motion,  they 
are  stationary  and  the  cans  revolve.  The  principle  is  similar 
to  that  of  the  vertical  ice  cream  freezer.  Heavy  iron  tanks,  with 
a  capacity  of  twelve  to  forty-eight  40-quart  cans,  are  used  for 
this  purpose.  The  bottoms  of  these  tanks  are  equipped  with  a 
system  of  cog  wheels,  set  in  motion  by  means  of  a  gear  at  one 
end  of  the  tank.  The  wheels  have  a  diameter  large  enough  to 
carry  one  can  each.  The  cans  are  set  on  these  wheels,  the  paddles 
are  inserted  and  fastened  to  cross-bars  and  the  power  started. 
The  cans  should  be  heavily  constructed  to  stand  rough  usage, 
without  suffering  indentations.  Cans  with  irregular,  depressed, 
or  bulged  sides  cause  the  paddles  to  do  poor  work.  Such  cans 
should  be  slipped  over  a  wooden  horn,  or  other  contrivance,  and 
the  indentations  hammered  out  with  a  mallet.  The  paddles  are 
held  stationary  by  cross-bars  and  are  forced  against  the  periphery 
of  the  cans  by  springs..  Attention  should  also  be  paid  to  the 
pivdts  on  which  the  cog  wheels  rest.  If  they  are  warped,  the 
wheels  do  not  run  true,  so>  that  it  is  not  possible  for  the  paddles 
to  scrape  the  sides  of  the  cans  properly. 

The  sweetened  condensed  milk  should  be  cooled  gradually. 
Sudden  chilling  should  be  avoided.  This  is  best  accomplished 
byt  warming  the  water  in  the  cooling  tank  to  about  90  degrees  F., 
before  the  cans  are  set  in.  The  cans  are  then  allowed  to  revolve 
for  fifteen  to  twenty  minutes  before  any  cold  water  is  turned 
into  the  tank.  After  that,  cold  water  is  turned  in  slowly  until 
the  temperature  of  the  milk  has  fallen  to  about  70  degrees  F,  The 


SWEETENED  CONDENSED  MILK — COOLING 


105 


Pig1.  35.     Cooling-  tank  for 
sweetened  condensed  milk 
Courtesy  Arthur  Harris  &  Co. 


It    is 


entire  time  of  cooling  should  last  about 
two  hours.  The  cans  should  revolve 
slowly,  rapid  stirring  enhances  the 
precipitation  of  sugar  crystals.  In  order 
to  scrape  the  sides  of  the  cans  efficient- 
ly, when  the  cans  revolve  slowly, 
(about  five  revolutions  per  minute)  it 
is  advisable  to  use  two  paddles  in  each 
can,  scraping  the  cans  at  opposite  sides. 
When  the  milk  is  sufficiently  cooled 
the  cans  are  stopped,  the  paddles  lifted 
out,  scraped  and  removed,  and  the 
cans  taken  out  of  the  tank.  This  me- 
thod of  cooling  sweetened  condensed 
milk  is  still  in  vogue  in  the  majority  of 
obviously  crude,  laborious  and  time-con- 


condenseries. 
su  ming. 

In  some  factories  the  condensed  milk  is  transferred  from 
the  pan  direct  into 
large  tanks  and  is  sub- 
sequently cooled  by 
pumping  it  with  a  high 
pressure  pump  through 
a  series  of  coils  sub- 
merged in  cold  water. 
This  method  is  labor 
and  time-saving  and 
the  objectionable  fea- 
tures of  agitation  are 
avoided.  On  the  other 
hand,  there  is  danger 
of  too  rapid  chilling, 
which  tends  toward  ex- 
cessive sugar  crystalli- 
zation and  the  produc- 
tion of  rough,  sandy 
and  settled  milk. 

Within  recent  years 

the  imp  of  circular  tank<;  ^*      Ti*-  3G-     Vertical  coil  cooler 

rcuiar  tanks        Courtesy  of  Jensen  Creamery  Machinery  Co. 


106  SWEF/TSNED    CONDENSED    MlIvK — CoOUNG 

with  jacket  and  vertically  suspended,  revolving  coil,  has  been 
adopted  in  numerous  factories  with  most  satisfactory  results, 
and  this  method  of  cooling  this  viscous  product  promises  to 
assist  in  solving  the  cooling  problem.  Rectangular  vats  with 
horizontal  coils,  which  also  have  been  tried  for  this  purpose, 
however,  are  less  desirable,  as  they  tend  to  cause  the  condensed 
milk  to  foam  excessively.  This  foaming  is  caused  by  the  fact 
that  the  horizontal  coil  revolves  into  the  milk,  beating  air  into 
it.  In  the  case  of  the  circular  tank,  the  vertical  suspended  coil 
wrhen  revolving  moves  upward,  out  of  the  milk,  thus  avoiding 
incorporation  of  air  and  excessive  foaming.  The  circular  vat 
with  the  suspended  vertical  coil  has  the  further  advantage  that 
the  condensed  milk  does  not  come  in  contact  with  bearings  and 
glands,  these  parts  being  entirely  detached  from  the  vat. 

A  still  more  recent  method  of  cooling  sweetened  condensed 
milk  consists  of  a  combination  of  the  use  of  the  submerged  coil 
and  subsequent  slow  agitation.  The  equipment  for  this  niethod 
consists  of  a  vertical  or  horizontal  tank,  equipped  writh  a  sub- 
merged coil.  This  coil  should  have  a  diameter  of  about  H 
inches  and  a  length  of  from  600  to  700  feet,  the  length  needed 
depending  on  the  temperature  to  which  it  is  desired  to  cool  the 
condensed  milk  and  the  temperature  of  the  cooling  water.  The 
coil  is  usually  of  regular,  so-called  sanitary  pipe  (copper  pipe 
tinned  on  inside)  or  it  may  be  black  iron  pipe  preferably  sand- 
blasted on  inside. 

-  The  submerged  coil  connects  at  its  intake  with  a  high  pres- 
sure pump  and  at  its  outlet  with  one  or  more  large  enameled 
steel  holding  tanks  (capacity  usually  5,000  gallons).  Each  of 
these  holding  tanks  is  equipped  with,  a  powerful  motor-driven, 
vertically  slanting  agitator,  also  enameled.  The  agitator  re- 
volves at  a  speed  of  about  12  R.  P.  M. 

In  the  operation  of  this  method  of  cooling,  the  hot  sweet- 
ened condensed  milk  is  drawn  from  the  vacuum  pan,  preferably 
by  gravity,  into  a  standardizing  vat  mounted  on  scales.  When 
all  the  condensed  milk  of  one  and  the  same  batch  has  been  trans- 
ferred to  this  tank  it  is  accurately  weighed.-  The  weight  of  the 
original  fluid  milk  is  then  divided  by  the  weight  of  the  con- 
densed milk.  This  yields  the  exact  ratio  of  concentration.  If 


CONDENSED  MILK — COOLING 


107 


Pig-.  37. 

Hig-h  pressure   pump  for  sweetened  condensed 
milk 

Courtesy  of  Union   Steam  Pump  Co. 


the  concentration  is  in  excess  of  that  desired,  the  product  is 
standardized  by  the  addition  of  the  accurately  calculated  nec- 
essary amount  of  distilled  water. 

From  this  stand- 
ardizing tank  the  hot 
condensed  milk  is 
forced  by  means  of  the 
high  pressure  pump 
through  the  submerged 
coil  in  the  cooling  tank. 
The  water  supply  to 
this  tank  is  automati- 
cally regulated  by  a 
thermostat,  so  as  to 
cool  the  condensed  milk 
to  the  desired  tempera- 
ture (usually  65  to  75  degrees  F.). 

The  condensed  milk  remains  in  the  submerged  coil  about 
six  minutes,  i.  e.,  six  minutes  elapse  from  the  time  it  enters 
the  coil  till  it  reaches  the  exit.  From  here  the  now  cool  con- 
densed milk  flows  to  the  holding  tank  where  it  is  slowly  agitated 
for  several  hours. 

Experience  has  demonstrated  that  this  method  of  cooling 
and  agitating  sweetened  condensed  milk  is  very  effective  in 
preventing  the  production  of  sandy  and  settled  milk.  It  appears 
that  the  great  viscosity  of  the  sweetened  condensed  milk  causes 
the  milk,  in  its  passage  through  the  coil,  to  be  subjected  to  the 
least  damaging  agitation.  The  center  of  the  column  of  the 
milk  moves  forward  slightly  faster  than  the  portion  nearest  the 
walls  of  the  coil.  This  results  in  a  rolling  or  curling  motion, 
producing  sufficient  and  yet  not  excessive  agitation. 

The  subseqent  slow  agitation  of  the  cooled  condensed  milk 
in  the  holding  tanks  for  a  considerable  period  of  time,  further 
assists  in  the  preservation  of  a  smooth  product.  It  enhances 
the  formation  of  very  small  crystals  at  the  expense  of  larger 
crystals,  thereby  minimizing  the  tendency  toward  coarseness  and 
insuring  a  uniformly  smooth  product  that  is  not  prone  to  yield 
a  sugar  sediment. 


108 


SWEETENED  CONDENSED  MILK — COOLING 


fi° 


CONDENSED  MILK — COOUNG  109 

The  pressure  required  to  pump  the  sweetened  condensed 
milk  through  the  cooling  coil  and  up  into  the  holding  tanks 
varies  from  about  800  to  1200  pounds,  and  the  pump  used  for 
this  purpose  must  be  strong  enough  to  develop  a  pressure  of 
at  least  2,000  pounds,  which  may  be  required  to  start  the  flow 
through  the  coil  after  the  milk  has  stood  idle  for  some  time  and 
has  become  chilled. 

This  method,  in  addition  to  its  labor-saving  feature,  and 
to  its  efficiency  in  avoiding  sandy  and  settled  condensed  milk, 
has  the  further  important  advantage,  that  the  product  is  pro- 
tected against  contamination  with  bacteria,  mold,  and  other  im- 
purities from  the  air.  etc.,  the  product  being  under  seal  until 
it  reaches  the  filling  machine,  or  until  it  is  packed  into  barrels 
in  the  case  of  bulk  goods.  This  method,  therefore,  should  be 
particularly  adapted  for  efforts  to  produce  an  article  that  does 
not  develop  "buttons"  with  age.  See  also  Chapter  on  "Defects 
of  Sweetened  Condensed  Milk." 

The  chief  criticism  that  may  be  raised  against  this  method 
lies  in  the  question  of  cleaning  the  cooling  coil.  From  the 
standpoint  of  bacterial  contamination  it  may  safely  be  said, 
however,  that  the  danger  of  such  contamination  is  remote.  After 
the  product  of  one  day's  make  has  passed  through  the  coil,  the 
coil  is  sealed  by  valves  and  there  is  no  reason  to  doubt  that 
the  condensed  milk  remaining  in  the  coil  till  next  day's  opera- 
tion, is  not  just  as  well  protected  against  all  contaminating 
influences,  as  if  it  were  sealed  in  tin  cans.  It  is  advisable,  how- 
ever, to  completely  empty  and  rinse  and  steam  the  submerged 
coil  at  regular  intervals  of  say  once  per  week.  This  is  especially 
desirable  in  the  case  of  a  copper  coil,  in  order  to  guard  against 
an  excessive  accumulation  of  copper  salts  which  would  tend 
to  lend  the  product  a  metallic  flavor  and  to  jeopardize  its  wrhole- 
someness.  In  the  case  of  a  black  iron  coil,  sand-blasted  on  inside, 
the  effect  of  the  action  of  the  acid  and  sugar  of  the  milk  is 
negligible.  However,  when  not  filled  with  condensed  milk  the 
iron  coil  should  be  kept  filled  with  clean  water  to  prevent  exces- 
sive rusting. 


110 


SWEETENED  CONDENSED  MILK — FILUNG 


CHAPTER  VII. 
FILLING. 

The  sweetened  condensed  milk  is  put  on  the  market  in 
barrels  and  in  hermetically  sealed  tin  cans. 

In  Barrels. — Barrels,  similar  to  glucose  barrels,  are  generally 
used.  They  hold  from  three  hundred  to  seven  hundred  pounds 
of  condensed  milk.  New  barrels  should  be  used  for  this  purpose. 
Barrels  paraffined,  or  coated  with  sodium  silicate,  on  the  inside 
are  most  satisfactory,  as  they  are  more  apt  to  be  free  from  mold 
spores.  Old  glucose  barrels  are  dangerous  to  use,  as  they  often 
contain  decaying  remnants  of  glucose,  which  cause  the  condensed 
milk  to  ferment.  The  new  barrels  are  steamed  out  and  drained 
thoroughly.  The  rilling  is  facilitated  by  the  use  of  a  large  gal- 
vanized iron  funnel  with  a  discharge  one  and  one-half  inches 
in  diameter,  or  an  ordinary  milk  pail  with  a  nipple  one  and  one- 
half  inches  in  diameter  in  the  bottom  of  the  pail.  When  filled^ 
a  double  layer  of  cheese  cloth  is  placed  over  the  bunghole,  and 
the  bung  is  driven  in  level  with  the  staves.  The  barrel  goods 
are  sold  to  bakeries  and  candy  factories. 

In  Cans. —The 
canned  goods  are  in- 
tended for  the  retail 
market.  The  cans 
used  hold  from  eight 
ounces  to  one  gallon 
of  condensed  milk. 
Most  makes  of  tin 
cans  for  sweetened 
condensed  milk  have 
a  small  opening, 
three-eighths  to  three- 
fourths  inch  in  diam- 
eter through  which 
they  are  filled.  The 
cans  known  and  sold 
under  the  trade  name  pi  39 

Sanitary     can        are       pilllng.  maclline  for  sweetened  condensed  milk 
filled    before    the    top  Courtesy  of  Schaefer  Mfg.  Co. 


SWEETENED  CONDENSED  MILK — 


111 


is  crimped  on.  Sweetened  condensed  milk  is  of  a  semi-fluid, 
viscous  and  sticky  consistency.  The  successful  and  rapid  filling 
of  the  cans  without  spilling  the  milk  over  the  top  of  the 
can  is,  therefore,  somewhat  difficult.  If  done  by  hand  the 
work  is  very  slow.  For  this  reason  many  ingenious  ma- 
chines have  been  devised  which  are  more  or  less  efficient 
in  "cutting  off"  the  milk  without  "slobbering."  The  filling 
machines  now  in  use  vary  from  the  primitive  hand  filler,  in 
which  the  condensed  milk  is  "ground  out"  by  the  turning  of 


Fig1.  40.     The  solder  seal 


Tig.  41.     The  Sanitary  can 


Fig*.  42.     The  Gebee  seal  Fig-.  43.     The  McDonald  seal 

a  crank  by  hand,  to  the  most  perfect  forms  of  automatic  filling 
machines.  In  these  filling  machines,  all  parts  coming  in  con- 
tact with  the  condensed  milk  are  constructed  of  brass.  They 
usually  are  equipped  with  a  reservoir,  receiving  tank,  or  hopper, 
which  has  an  automatic  feed,  usually  a  floating  device  attached 
to  a  valve,  which  regulates  the  inflow  according  to  the  discharge. 
The  discharge  is  adjustable  to  fill  any  size  can  with  a  remarkable 
degree  of  accuracy,  except  gallons  which  are  usually  filled  by 


112  SWEETENED  CONDENSED  MILK — SEALING 

• 

hand.     Machines  of  this  type  will  fill  from  twenty-five  thousand 
to  thirty  thousand  cans  per  day  (ten  hours). 

These  machines  are  of  complex  construction  and  must  re- 
ceive proper  care.  It  is  best  to  clean  them  thoroughly  after  each 
day's  work.  But,  since  their  inlet  and  discharge  are  closed  her- 
metically, the  complete  washing  may  be  done  once  per  week 
only,  without  seriously  disturbing  their  efficiency, or  impairing 
the  product.  For  thorough  cleaning,  the  filler  should  be  dis- 
sected, removing  all  detachable  parts,  such  as  valves,  pistons, 
tubes,  etc.  When  freed  from  all  remnants  of  condensed  milk, 
the  parts  should  be  scalded,  dried  and  replaced  in  the  machine. 
In  order  to  guard  against  all  possible  contamination  by  remnants 
of  wash  water,  it  is  advisable  to  reject  the  first  few  cans  of  milk 
of  the  next  filling.  When  not  in  use,  the  filling  machine  should 
be  covered  with  clean  cloth,  or  oil  cloth,  to  protect  it  from  dust 
and  flies,  etc. 

As  soon  as  the  cans  are  filled,  they  should  be  "capped."  If 
allowed  to  stand  open,  dust,  dirt  and  flies,  or  other  insects  are 
prone  to  reach  their  interior,  and  the  prolonged  exposure  of  the 
condensed  milk  to  the  air  and  light  causes  the  surface  to  crust 
over  and  to  develop  a  tallowy  flavor. 

SEALING. 

Kinds  of  Seals. — The  seal  must  be  air-tight  and  firm  enough 
to  prevent  its  breaking  during  the  rough  treatment  to  which  the 
cans  are  exposed  in  transportation.  There  are  several  methods 
of  sealing  the  cans,  depending  largely  011  the  construction  of  the 
can.  *  Most  of  the  cans  used  are  sealed  with  solder.  There  is  a 
groove,  around  the  opening,  the  periphery  of  the  cap  fits  into  this 
groove  and  the  latter  is  filled  with  solder.  In  the  case  of  cans 
which  are  sealed  without  solder,  the  cap  or  the  entire  end  of  the 
can  is  crimped  onto  the  can  so  as  to  make  a  hermetical  seal.  The 
McDonald  seal  with  the  friction  cap,  the  Gebee  seal  with  the  burr 
cap,  and  the  Sanitary  can  seal  with  the  top  of  the  can  crimped  on 
after  filling,  are  the  chief  types  of  solderless  seals.  In  the  case  of 
the  McDonald  seal,  a  tightly  fitting  cap  with  a  wide  flange  is 
pressed  into  the  opening.  The  "capped"  can  passes  under  a 
series  of  steel  rollers  pressing  the  flange  firmly  against  the  top  of 


CONDENSED  MILK — SEALING 


113 


the  can.  This  seal  is  very  simple,  but  is  not  very  strong  and 
not  hermetically  tight.  In  the  case  of  the  Gebee  seal,  a  rim  pro- 
jects around,  the  opening  of  the  can.  After  the  cap  is  inserted, 
it  is  crimped  over  this  rim  by  means  of  a  series  of  revolving  dies. 
This  seal  is  reasonably  strong  but  not  hermetically  tight.  The 
Sanitary  can  is  entirely  open  at  one  end  when  filled.  The  cover 
or  end  is  crimped  around  the  periphery  of  the  body  of  the  can 
by  means  of  revolving  dies.  This  seal  is  reasonably  strong 
and  usually  hermetically  tight.  The  chief  advantages  of  the 
seals  without  solder  lie  in  the  saving  of  labor  and  the  reduction 
of  the  cost  due. to  the  omission  of  solder. 

Soldering  Devices  and  Machinery. 
—The  sealing  of  all  solderless  seals  is 
done  by  specially   constructed   sealing 
machines. 


Fig*.  44.     Soldering-  stove 
Courtesy  of  Arthur  Harris  &  Co. 

For  seals  with  solder  there  are  sev- 
eral machines  on  the  market  but  much 
of  this  work  is  as  yet  done  by  hand. 
For  this,  different  types  of  soldering 
coppers  are  in  use  and  the  copper  tips 
are  heated  in  soldering  stoves  or  pots. 
Some  soldering  coppers  have  hollow 
circular  tips  with  a  diameter  equal  to 
that  of  the  cap  used.  The  hollow  tip 
is  telescoped  by  a  rod  which  holds  the, 
cap  in  place  and  the  periphery  of  the  tip  fits  into  the  groove 
of  the  opening  of  the  can,  where  it  melts  the  solder.  A  rapid, 
neat  and  leakless  seal  can  be  made  with  this  instrument. 

Ordinary  soldering  coppers  with  a  blunt  point,  such  as  are  in 


Pig-.  45.    A  convenient  de- 
vice for  soldering  by  hand 


114  SWEETENED  CONDENSED  MILK — SEAUNG 

genera!  use  by  the  tin  smith,  are  not  very  satisfactory.  Unless 
they  are  drawn  out  and  filed  down  into  a  fine  point,  their  use  is 
not  conducive  of  neat  work,  progress  is  comparatively  slow  and 
leakers  are  often  numerous.  When  gas  is  available  the  automatic 
soldering  copper  may  be  used  to  advantage.  In  this  tool  the 
copper  tip,  which  is  long  and  slender  is  automatically  heated  by 
a  current  of  gas  passing  through  the  handle  and  burning  at  the 
copper  tip.  The  handle  of  the  device  is  connected  with  the  gas 
and  air  pipes  by  means  of  flexible  rubber  tubing.  No  time  is 
lost  waiting  for  the  copper  to  heat  and  the  flame  can  be  so 
regulated  that  the  temperature  of  the  copper  tip  is  right  and 
uniform.  This  is  important,  because  perfect  work  is  impossible 
unless  the  coppers  have  the  proper  temperature. 

Machine-soldering  is  now  rapidly  replacing  hand-soldering. 
The  principle  of  the  older  types  of  soldering  machines-  consisted 
of  revolving  discs  on  which  the  tin  cans  were  placed.  The  cap 
was  held  in  place  by  a  vertical  rod  pressing  on  it.  The  solder 
was  applied  by  hand,  the  hot  soldering  copper  was  held  over 
the  groove  in  the  can  while  the  cans  revolved.  This  method  had 
no  particular  advantage  over  the  hand  soldering.  There  was 
little,  if  any,  saving  of  time  and  the  quality  of  the  work  was  not 
much,  if  any.  better. 

There  are  now  on  the  market  newer  types  of  soldering  ma- 
chines, most  ingeniously  constructed  and  their  operation  in  fac- 
tories with  large  outputs  economizes  labor  and  time. 

Solder. — The  solder  used  for  sealing  should  be  of  standard 
composition.  In  this  country,  canning  establishments  are  prone 
to  use  a  very  poor  quality  of  solder.  It  contains  from!  45  to  55 
per  cent  lead.  Lead  is  a  poisonous  metal ;  its  use  in  the  canning- 
industry  should,  therefore,  be  regulated  by  law.  In  Germany, 
the  law  requires  that  solder  used  in  tin  cans  for  food  products 
must  not  contain  over  10  per  cent  of  lead. 

Where  the  sealing  is  done  by  hand  the  solder  is  most  con- 
veniently used  in  the  form  of  thin  bars  or  wire.  The  wire  is 
usually  bought  already  cut  up  in  segments,  each  segment  furnish- 
ing solder  enough  to  seal  one  can.  In  the  newer  types  of  sol- 
dering machines  the  solder  wire  is  automatically  fed  from  spools. 


SWEETENED  CONDENSED  MILK — SEALING  115 

The  smaller  the  opening  of  the  can,  the  less  solder  is  necessary 
to  complete  the  seal.  An  opening  smaller  than  three-eighths  of 
an  inch  in  diameter,  however,  cannot  conveniently  be  used,  owing 
to  the  difficulty  of  rilling  the  can  with  this  viscous  product.  The 
essential  points  of  satisfactory  sealing  are:  no  ''leakers,"  neat 
work,  rapid  work,  small  amount  of  solder.  Aside  from  the  size 
of  the  opening  of  the  can.  the  amount  of  solder  used  depends 
on  the  experience  of  the  sealer.  Beginners  usually  make  an  un- 
even seal,  waste  much  solder,  and  have  many  "leakers."  This 
is  largely  due  to  their  ignorance  of  the  proper  soldering  tempera- 
ture of  the  copper.  An  experienced  sealer  will  use  from  two 
to  three  pounds  of  solder  per  thousand  tin  cans  with  moderate- 
sized  openings.  He  will  seal  from  fifteen  hundred  to  twenty-five 
hundred  cans  per  day. 

Soldering  Flux. — The  use  of  solder  requires  the  application 
of  soldering  flux,  to  prepare  the  surface  of  the  tin  for  the  solder. 
The  flux  always  precedes  the  solder.  When  the  hot  solder  is 
applied,  some  of  the  flux  is  bound  to  sweat  through,  between  cap 
and  can.  gaining  access  to  the  interior  of  the  can.  The  common 
practice  of  using  zinc  chloride  or  other  similar  acid  fluxes,  which 
are  highly  poisonous,  therefore,  cannot  be  too  strongly  con- 
demned. Their  presence  in  the  can  may  jeopardize  the  health 
and  life  of  the  consumer,  as  well  as  the  marketable  properties  of 
the  product.  There  are  other  fluxes  which  are  absolutely  harm- 
less, and  which,  if  properly  used,  give  satisfactory  results.  Dry, 
powdered  resin,  or  resin  dissolved  in  alcohol  or  gasoline,  are  of 
this  class.  Ammonium  chloride,  while  used  in  most  tin  shops, 
is  not  as  well  suited  for  this  purpose. 

Gas  Supply.— A  plentiful  and  steady  supply  of  gas  is  very 
essential.  Where  natural  gas  or  gas  from  a  municipal  corpora- 
tion is  not  available,  the  factory  must  rely  on  its  own  generator. 
For  the  needs  of  the  condensery  a  gasoline  gas  plant  seems 
suitable.  Gasoline  gas  is  produced  by  forcing  atmospheric  air 
over  or  through  a  body  of  gasoline.  The  mixture  of  air  and 
gasoline  vapors  forms  the  gasoline  gas.  The  gas  generators  in 
use  consist  chiefly  of  carburetor,  air  pump  or  blower,  and  regu- 
lator. The  carburetor  usually  has  a  series  of  cells,  connected 
with  one  another  by  means  of  a  system  of  syphon  tubes.  The 


116  SWEETENED   CONDENSED    MlI^K — $EAIJNG 

interior  of  each  cell  is  partitioned  off  with  heavy  cotton  wicking 
This  wicking  absorbs  the  gasoline  by  capillary  attraction.  The 
air,  passing  through  the  fine  meshes  of  wicking,  comes  in  contact 
with  a  large  surface  of  gasoline. 

The  following  are  some  of  the  essential  points  to  be  observed 
in  the  installation  and  operation  of  gas  generators  of  this  type: 
Sink  the  carburetor  low  enough  (three  to  five  feet  below  the 
surface  of  the  ground  if  necessary)  to  permit  the  gas  pipe  to  slant 
from  the  factory  to  the  carburetor.  If  the  gas  pipe  is  horizontal, 
or  inclined  toward  the  factory,  condensation  water  may  collect 
in  the  pipe,  obstructing  the  free  passage  of  gas.  This  causes  the 
gas  either  not  to  be  available  at  all,  or  to  reach  the  stoves  in 
irregular  gusts,  which  is  equally  unsatisfactory.  Where  the  gas 
pipe  slants  toward  the  carburetor,  the  condensation  water  flows 
back  into  the  carburetor,  causing  no  obstruction.  Use  gasoline 
of  the  best  quality  only.  Cheap  grades  form  a  residue  and  clog 
the  generator.  The  gasoline  is  best  bought  in  iron  barrels ;  this 
prevents  unnecessary  loss  by  evaporation,  which  occurs  in 
wooden  barrels,  especially  in  summer.  The  cells  should  not  be 
filled  more  than  two-thirds  full ;  too  much  gasoline  reduces  the 
gas-generating  capacity  of  the  carburetor.  If,  during  extremely 
cold  weather,  the  carburetor  refuses  to  generate  gas,  the  injection 
of  a  pint  of  wood  alcohol  through  the  blow  pipe  into  the  cells, 
usually  remedies  the  trouble.  The  gas  plant  and  gasoline  storage 
should  be  located  in  a  separate  building  and  at  a  reasonable 
distance  from  the  main  building,  in  order  to  minimize  danger 
from  fire. 


PART  III 

MANUFACTURE  OF  UNSWEETENED  CON- 
DENSED  MILK 

EVAPORATED  MILK 

CHAPTER  VIII. 
DEFINITION. 

There  are  three  kinds  of  unsweetened  condensed  milk  on 
the  market,  namely,  evaporated  milk,  formerly  called  evaporated 
cream,  plain  condensed  bulk  milk  and  concentrated  milk. 

Evaporated  milk  is  cow's  milk  condensed  in  vacuo  at  the 
ratio  of  about  two  to  two  and  one-half  parts  of  fresh  milk  to  one 
part  of  condensed  milk.  It  is  of  the  consistency  of  thin  cream 
and  reaches  the  market  in  hermetically  sealed  cans  varying  in 
size  from  eight  ounces  to  one  gallon.  Evaporated  milk  is  pre- 
served by  sterilization  in  steam  under  pressure.  When  properly 
made,  it  will  keep  indefinitely,  but  is  best  when  fresh. 

QUALITY  OF  FRESH  MILK. 

In  the  manufacture  of  evaporated  milk  the  physiological 
normality  and  the  chemical  purity  and  sweetness  of  the  fresh 
milk  are  factors  even  more  important  than  in  the  case  of  sweet- 
ened condensed  milk.  A  uniformly  satisfactory  and  marketable 
product  cannot  be  manufactured,  unless  the  milk  is  normal  and 
pure  in  every  respect.  The  reason  for  this  largely  lies  in  the 
fact,  that  defects  the  fresh  milk  may  have,  are  greatly  magnified 
and  intensified  by  the  high  sterilizing  temperature  to  which  the 
evaporated  milk  is  subjected.  While,  from  the  biological  point 
of  view,  contaminations  of  this  milk  are  largely  rendered  harm- 
less by  sterilization,  defective  fresh  milk  cannot  be  made  into 
a  marketable  product,  because  such  milk  usually  does  not  survive 
the  process. 

It  should  be  understood  that  any  condition  or  factor  that, 
in  the  slightest  degree,  increases  the  tendency  or  ability  of  the 


118  EVAPORATED  MII<K — HEATING 

casein  to  curdle,  tends  toward  the  formation  of  a  hard,  unshak- 
able coagulum  during  sterilization,  and  makes  the  manufacture 
of  a  marketable  product  difficult.  Abnormal  milk  of  this  type 
may  come  from  cows  approaching  parturition,  or  too  soon  after 
calving,  or  milk  from  cows  suffering  from  disease,  generalized 
or  local,  or  from  cows  in  poor  and  abnormal  physical  condition 
which  may  be  brought  about  by  poor  care,  over-feeding,  feeding 
the  wrong  kinds  of  feed,  or  feed  in  poor  condition,  exposure  to 
abnormally  hot  weather  and  flies,  or  any  other  condition  which 
disturbs  the  physiological  functions  of  the  animal  and  thereby 
affects  the  physical,  chemical,  and  physiological  properties  of 
the  milk;  or  it  may  be  due  to  improper  care  of  the  milk,  causing 
it  to  be  excessively  contaminated  with  germ  life,  or  to  be  rel- 
atively high  in  acid.  All  such  milk  renders  the  quality  of  the 
finished  product  uncertain  and  may  result  in  heavy  loss. 

In  view  of  these  facts  it  is  obvious  that  the  greate'st  care 
should  be  exercised  on  the  receiving  platform,  inspecting  every 
can  of  milk,  using  the  most  reliable  means,  as  recommended  in 
Chapter  III  on  "Control  of  Quality,"  to  detect  suspicious  milk, 
and  rejecting  all  m'ilk  that  fails  to  reach  the  sanitary  standard 
adopted  by  the  factory. 

Standardizing. — In  order  to  insure  in  the  finished  product 
the  percentage  relation  of  fat  to  solids  not  fat  that  meets  with 
the  Federal  Standard  or  with  any  other  standard  desired,  the 
fluid  milk  should  be  accurately  standardized.  For  this  purpose 
each  batch  of  fluid  milk  must  be  correctly  tested  for  per  cent  fat 
and  per  cent  solids  not  fat.  On  the  basis  of  these  tests,  the 
amount  of  cream  or  skim  milk  which  it  is  necessary  to  remove 
or  to  add,  as  the  case  may  be,  can  then  be  readily  calculated. 
For  detailed  directions  on  standardizing  the  milk  to  any  desired 
standard  see  Chapter  XXIX  on  "Standardization." 

HEATING  THE  MILK. 

The  equipment  for  heating  the  milk  should  be  such  as  to 
enable  the  factory  to  heat  the  milk  with  the  least  possible  delay 
so  as  to  avoid  the  development  of  acid,  or  to  make  possible  the 
prompt  cooling  of  the  milk  upon  its  arrival  to  a  temperature  at 
which  bacterial  development  is  checked.  In  the  manufacture  of 
evaporated  milk,  the  batches  of  condensed  milk  in  the  vacuum 


EVAPORATED  MILK — CONDENSING  119 

pan  must  be  relatively  small.  This  milk  foams  more  in  the  pan 
than  the  heavier  sweetened  condensed  milk.  This  factor  reduces 
therefore,  the  capacity  of  the  pan.  If  the  milk  is  not  cooled  upon 
arrival,  but  is  transferred  immediately  to  the  hot  wells,  it  is 
advisable  to  use  numerous  small  wells,  rather  than  but  one  or 
a  few  large  ones.  These  small  wells  fill  rapidly  and  the  milk 
can  be  heated  without  delay.  This  system  makes  it  possible  to 
render  the  bacteria  inactive  and  harmless  practically  as  soon 
as  the  milk  arrives,  minimizing  the  danger  of  acid  formation.1 
Steam  may  be  saved  if  the  milk  is  forewarmed  by  running 
it  through  coils  inclosed  in  a  chamber  of  exhaust  steam,  but  the 
coils  increase  the  labor  and  difficulty  of  cleaning.  It  is  best  to 
heat  the  milk  to  as  near  the  boiling  point  as  possible  and  hold 
it  there  for  five  to  ten  minutes,  provided  that  the  capacity  of  the 
factory  warrants  this  delay.  In  this  heating  the  casein  ot  the 
milk  is  somewhat  changed.  There  occurs  partial,  though  invis- 
ible, precipitation,  and  the  higher  the  temperature  to  which  the 
milk  is  heated,  the  more  pronounced  is  this  change.  This  change 
is  desirable,  because  the  casein  thereby  surrenders,  to  a  limited 
extent,  its  power  and  tendency  to  form  a  firm  curd  in  the  ster- 
ilizer. See  also  Chapter  XI  on  " Sterilizing." 

CONDENSING. 

The  same  apparatus,  the  vacuum  pan  and  pump,  is  used 
for  condensing  the  milk,  and  the  process  of  condensing  is  prin- 
cipally the  same,  as  in  the  case  of  sweetened  condensed  milk. 
The  fresh  milk  is  condensed  at  the  ratio  of  two  to  two  and  one- 
half  parts  of  fresh  milk  to  one  part  of  condensed  milk.  In  some 
factories  it  is  customary  to  superheat  the  milk  in  the  pan  before 
it  is  drawn  off,  i.  e.,  the  steam  to  the  jacket  and  coils  is  shut  off, 
the  water  valve  is  closed,  the  vacuum  pump  is  stopped  and 
"live"  steam  is  passed  into  the  condensed  milk.  When  the 
vacuum  has  dropped  to  about  six  to  eight  inches,  and  the  tem- 
perature has  risen  to  180  to  200  degrees  F.  the  superheating  is 
stopped,  the  steam  is  turned  off,  the  vacuum  pump  is  started 
again,  and  the  condensing  is  completed.  The  superheating  is  fre- 
quently also  done  after  the  evaporated  milk  has  been  drawn 

1  See  also  Cooling  Milk  and  Standardization. 


120  EVAPORATED  MILK — STRIKING 

from  the  pan.  In  this  case,  the  process  of  evaporation  is  usually 
carried  slightly  beyond  the  desired  density  of  the  finished  prod- 
uct, the  evaporated  milk  is  drawn  from  the  pan  into  an  open  vat 
or  kettle  where  steam  is  turned  direct  into  the  milk  until  the 
superheating-  is  completed,  which  is  indicated  by  its  greater  con- 
sistency and  the  slightly  flaky  condition  of  the  curd.  Then  water 
is  added  to  the  superheated  evaporated  milk  to  bring  the  product 
back  to  the  desired  density. 

The  chief  purpose  of  superheating  is  to  partly  precipitate 
the  curd.  This  minimizes  the  danger  of  the  formation  of  too 
hard  a  curd  in  subsequent  sterilization.  It  also  lends  the  body 
of  the  milk  the  appearance  of  greater  consistency,  gives  it  a 
more  creamy  character  and  assists  in  the  prevention  of  sub- 
sequent fat  separation.  The  superheating  of  evaporated  milk  is 
not  essential  for  the  production  of  quality  and  marketable  prop- 
erties, but  it  is  looked  upon  by  many  manufacturers  as  a  safe- 
guard against  such  defects  as  curdiness  and  fat  separation.  It 
is  not  improbable  that  its  advantages  are  much  overestimated, 
and  in  most  factories  the  superheating  process  in  entirely  omitted. 

The  condensing  of  milk  for  the  purpose  of  manufacturing 
evaporated  milk  may  be  done  also  in  the  absence  of  the  vacuum 
pan,  by  the  use  of  the  "Continuous  Concentrator,"  the  construc- 
tion and  operation  of  which  are  described  in  Chapter  XIV  on 
"Condensing  by  Continuous  Process." 

STRIKING. 

The  striking,  or  sampling  and  testing  for  density,  of  evapor- 
ated milk,  is  more  easily  accomplished  than  that  of  the  swreetened 
condensed  milk.  When  this  product  has  nearly  reached  the 
proper  density,  it  is  not  viscous  and  syrupy,  containing  no  cane 
sugar.  It  resembles  in  consistency  rich  milk  or  thin  cream  and 
has  a  specific  gravity  of  1.05  to  1.075  at  15.5  degrees  C.  or  60 
degrees  F. 

Samples  are  drawn  from  the  vacuum  pan  as  described  under 
sweetened  condensed  milk  and  the  density  can  be  readily  deter- 
mined by  means  of  a  hydrometer.  Beaume  hydrometers,  register- 
ing from!  5  to  15  degrees  B.,  are  generally  used.  As  it  is  im- 
portant that  the  determinations  be  accurate,  the  hydrometer 


EVAPORATED  MILK — STRIKING  121 

should  he  sensitive  and  its  scale  should  he  subdivided  into  tenth 
degrees.  The  hatch  should  he  "struck"  at  a  uniform  tempera- 
ture, say  120  degrees  F.,  so  as  to  avoid  misleading  readings  of 
the  hydrometer.  A  difference  of  a  few  tenths  degrees  Beaume 
affects  the  behavior  of  the  evaporated  milk  in  the  sterilizer  very 
appreciably.  If  the  density  is  too  great  the  product  may  badly 
curdle  during  sterilization.  If  the  density  is  too  low  the  evapor- 
ated milk  may  be  below  the  legal  standard.  It  is  advisable  for 
the  operator  to  use  a  pail  of  water  of  the  proper  temperature, 
when  he  strikes  the  batch,  so  that  he  can  adjust  the  temperature 
of  the  milk  in  the  hydrometer  jar  readily  and  quickly,  and  need 
not  depend  entirely  on  the  temperature  of  the  milk  in  the  pan 
which  may  change  several  degrees  while  he  is  engaged  in  the 
operation  of  striking.  The  hydrometer  jar  containing  the  sample 
of  evaporated  milk  is  set  into  the  pail  of  hot  water  of  the  desired 
temperature,  the  hydrometer  is  inserted  in  the  jar  and  the- read- 
ing is  taken. 

While  the  Beaume  hydrometers  should  be  used  at  the  tem- 
perature for  which  they  are  graduated,  which  is  60  degrees  F., 
they  answer  all  practical  purposes  at  any  other  temperature: 
at  120  degrees  F.  for  instance.  The  chief  essential  is  to  take  the 
reading  at  some  uniform  and  definite  temperature  and  read  the 
Beaume  at  that  same  temperature  in  the  case  of  every  batch.  In 
that  way  the  results  are  comparable.  The  operator  soon  learns, 
that  at  a  given  temperature  the  evaporated  milk  of  proper  den- 
sity shows  a  certain  Beaume  reading.  When  the  reading  is 
higher  or  lower,  the  milk  has  either  been  condensed  too  much  or 
not  enough.  The  use  of  the  automatic  "striker"  described  under 
"Striking  Sweetened  Condensed  Milk,"  practically  solves  the 
control  of  the  temperature  of  the  sample  taken. 

The  same  formula,  however,  cannot  be  used  under  all  con- 
ditions. No  rule-of-thumb  method  of  determining  the  density 
can  therefore  be  established.  Aside  from  the  degree  of  conden- 
sation, the  specific  gravity  of  the  milk  varies  with  locality,  season 
of  year,  quality  of  milk.  etc.  This  means  that  what  is  the  proper 
Beaume  reading  in  one  locality,  or  at  one  season  in  the  same 
locality,  may  be  entirely  wrong  in  another  locality,  or  at  other 
seasons  in  the  same  locality.  If  uniformity  in  the  density  and 
behavior  of  the  batches  of  evaporated  milk  is  to  be  secured 


122  EVAPORATED  MILK  —  STRIKING 

throughout  the  year,  the  operator  must  watch  the 
behavior  of  his  milk  from  day  to  day  and  from 
season  to  season  and  he  must  modify  the  Beaume 
reading  in  accordance  with  the  changing  conditions, 
This  is  one  of  the  all  important  stages  of  manufac- 
ture, w'here  relentless  and  careful  study  and  watch- 
fulness are  indispensable. 

In  order  to  make  absolutedy  sure  that  the  den- 
sity of  the  evaporated  milk  is  right,  it  is  advisable 
to  get  it  just  as  near  right  as  possible  in  the  pan 
and  then  draw  the  milk  from  the  pan  into  a  stand- 
ardizing vat,  large  enough  to  accommodate  the 
entire  batch  or  several  batches.  The  operator  then 
tests  the  milk  again  and  this  second  estimation  he 
can  perform  more  carefully,  because  he  is  then 
relieved  of  the  responsibility  of  attending  to  the 
operation  of  the  vacuum  pan.  If  the  evaporated 
milk  happens  to  be  a  trifle  too  heavy  he  can  dilute 
it  with  distilled  water  until  the  Beaume  reading 
is  just  right.  See  also  "Standardization,"  Chapter 
XXIX.  For  maximum  uniformity  and  accuracy 
of  results  of  determination  with  the  Beaume  hydro- 
meter, or  by  other  means,  it  is  essential  that  the  per- 
centage relation  of  fat  to  solids  be  uniform  from 
batch  to  batch.  This  uniformity  requires  standardi- 
zation of  each  batch. 

Correction  of  Beaume  Reading  at  Temperatures 
Other  than  60  Degrees  F.  —  At  a  temperature  of  120 
degrees  F.  the  Beaume  reading  of  the  finished  batch 
of  standard  evaporated  milk  may  vary  between 
about  6  and  8  degrees  B.,  according  to  season  of 
year  and  locality.  At  60  degrees  F.  the  Beaume 
reading  is  approximately  1.88  degrees  B.  higher. 

If  it  is  desired  to  record  the  Beaume  reading 
rig  46  at  *ke  correct  temperature,  i.  e.,  60  degrees  F.,  and 


hydro-  it  is  not  convenient  to  cool  the  evaporated  milk  to 
meter  for 
evaporated     that  temperature,  the  reading  at  any  temperature 

Courtesy  of     mav  be  corrected  as  follows:    when   the  tempera- 


C  JMtSC**Ue  *ure  at  which  the  Beaume  reading  is  taken  is  above 


EVAPORATED  MILK — STRIKING  123 

60  degrees  F.,  multiply  the  difference  between  the  temperature 
of  the  observed  reading  and  60  by  the  factor  .0313  and  add  the 
product  to  the  observed  reading. 

Example:  Beaume  at  120  degrees  F.  is  6.8;  what  is  the 
reading  at  60  degrees  F.  ? 

Answer:    6.8  -f  (60  X  -0313)  =  8.68  degrees   B. 

The  corrected  Beaume  reading  is  8.68  degrees  B.  When  the 
temperature  at  which  the  reading  is  made  is  below  60  degrees 
F.,  multiply  the  difference  between  the  temperature  of  the  ob- 
served reading  and  60  by  the  factor  .0313  and  subtract  the  prod- 
uct from  the  observed  reading. 

Calculation  of  Specific  Gravity  from  Beaume  Reading. — In 
order  to  record  the  density  of  the  evaporated  milk  in  terms  of 
specific  gravity,  instead  of  Beaume  degrees,  the  following  for- 
mula may  be  used : 

145.5 
Specific  gravity  —      AC  -  '"  p    ',  B  =  Beaume  reading  at  60 

degrees  F. 

Example:  Beaume  reading  at  60  degrees  F.  is  8  degrees  B. 
What  is  the  specific  gravity? 

145  5 

Specific  gravity  =    .  ,..  e  ' — 5-  =  1.0582 
14t).j  —  o 

Standardizing  Evaporated  Milk. — As  previously  suggested  it 
is  advisable  to  carry  the  condensing  process  slightly  beyond  the 
concentration  desired,  so  as  to  enable  the  operator  to  readily 
standardize  it  to  the  exact  point  desired  by  the  addition  of  a 
small  amount  of  distilled  water. 

As  soon  as  condensation  is  completed  the  contents  of  the 
pan  are  drawn  into  a  standardizing  vat  resting  on  scales.  The 
evaporated  milk  is  accurately  weighed ;  the  degree  of  concentra- 
tion is  calculated  by  divfding  the  weight  of  the  original  fluid 
milk  by  the  weight  of  the  evaporated  milk,  and  the  amount  of 
water  necessary  to  bring  the  solids  and  fat  to  the  exact  stand- 
ard desired  is  calculated,  and  added  to  the  evaporated  milk.  If 
it  is  desired  to  further  check  these  results,  or  instead  of  weigh- 
ing the  evaporated  milk,  it  may  be  tested  for  fat  and  solids,  and 
the  degree  of  concentration  may  be  calculated  by  dividing  the 
per  cent  of  fat  or  of  solids  in  the  evaporated  milk  by  the  per 
cent  of  fat  or  of  solids,  respectively,  in  the  fluid  milk.  For  de- 


124  EVAPORATED  MILK — HOMOGENIZING 

tailed  directions  on  calculations  of  concentration  and  on  exact 
method  for  standardizing-,  the  reader  is  referred  to  Chapter 
XXIX  on  "Standardization." 

CHAPTER  IX. 
HOMOGENIZING. 

Purpose. — The  object  of  homogenizing  is  to  avoid  the  separa- 
tion of  the  butterfat  in  the  evaporated  milk  after  manufacture. 

The  butter  fat  is  present  in  milk  in  the  form,  of  minute 
globules.  These  fat  globules  are  lighter  than  the  rest  of  the 
ingredients  of  the  milk.  They,  therefore,  show  a  strong  ten- 
dency to  rise  to  the  surface  and  to  form  a  layer  of  thick  cream 
in  the  cans.  When  these  cans  are  subsequently  subjected  to 
agitation,  as  is  the  case  in  transportation,  this  cream  churns, 
forming  lumps  of  butter.  This  tendency  of  evaporated  milk  to 
separate  in  storage  and  churn  in  transportation  is  especially 
noticeable  with  milk  rich  in  fat  and  in  which  the  large  fat  glob- 
ules predominate.  In  Jersey  and  Guernsey  localities,  it  is  more 
difficult,  therefore,  to  manufacture  evaporated  milk  that  does  not 
separate,  than  in  Holstein  and  Ayrshire  localities.  While  sepa- 
rated and  churned  evaporated  milk,  is  perfectly  sound  and  in 
every  way  as  valuable  as  a  food,  as  it  would  be  without  this 
separation,  it  does  not  sell  in  this  condition.  It  is  rejected  on 
the  market. 

This  tendency  toward  fat  separation  can  be  minimized  and 
frequently  entirely  prevented  by  increasing  the  viscosity  of  the 
evaporated  miilk.  This  can  be  accomplished  by  superheating  the 
milk  in  the  pan  or  after  it  leaves  the  pan,  and  by  prolonging 
the  sterilizing  process,  raising  the  heat  very  slowly  or  stopping 
the  reel  of  the  sterilizer  at  certain  stages  of  the  process.  How'- 
ever,  there  are  conditions  when  even  these  precautions  do  not 
permanently  avoid  separation  of  the  fat.  In  such  cases,  the 
proper  use  of  the  homogenizer  furnishes  a  reliable  means  to 
guard  against  this  difficulty. 

Principle  of  the  Homogenizer. — The  principle  of  the  homo- 
genizer is  to  force' the  milk  under  high  pressure  through  exceed- 
ingly small,  microscopic  openings.  By  so  doing  the  fat  globules 
are  broken  up  so  finely  that  they  fail  to  respond  to  the  gravity 


EVAPORATED  MILK — HOMOGENIZING  125 

f 

force,  they  cannot  rise  to  the  surface  and  therefore  remain  in 
homogeneous  emulsion.  The  value  of  the  homogenizer  lies  in 
removing  the  fundamental  cause  of  this  separation.  It  reduces 
the  fat  globules  to  such  small  size  that  their  buoyancy,  or  grav- 
ity force,  is  not  great  enough  to  overcome  the  resistance  of  the 
surrounding  liquid. 

The  earlier  theories  concerning  the  action  of  the  homogen- 
izer were  that  the  milk  had  to  pass  through  openings  so  mi- 
nute, that  the  fat  globules,  in  order  to  be  able  to  pass  through, 
were  crushed,  torn  and  divided  into  much  smaller  units,  hence 
their  fine  state  of  division  in  the  homogenized  milk. 

Later  study  of  the  principles  of  homogenization  has  revealed 
facts  and  probabilities  which  do  not  bear  out  the  earlier  assump- 
tions. Men  who  have  subjected  the  construction  and  operation 
of  homogenizers  to  intensive  study  claim,  that  the  openings  or 
orifices  through  which  the  milk  passes  in  the  machines  in  com- 
mercial use  when  operating  at  capacity,  range  in  size  from  about 
.003  inch  to  .01  inch.  If  these  findings  are  correct,  then  it  is  ob- 
vious that  the  fat  globules  and  even  clusters  of  fat  globules  can 
pass  through  the  homogenizer  as  entire  units  and  without  being- 
broken  up,  for  the  average  fat  globule  measures  about  .0001  inch 
in  diameter. 

It  is  not  improbable  that  the  homogenizing  action  is  very 
similar  in  its  atomizing  cause  and  effect,  as  that  which  takes 
place  in  the  spray-drying  process,  only  the  homogenizing  action 
is  more  intensive  because  of  the  smaller  size  of  the  openings 
through  which  the  milk  must  pass.  The  atomized  spray  in 
the  spray-drying  process  is  formed,  not  in  the  spray  nozzle,  but 
as  soon  as  the  pressure  is  released,  or  as  soon  as  the  millc 
escapes  from  the  nozzle. 

In  the  case  of  the  spray-drying  process,  the  atomized  spray 
is  discharged  into  a  medium  of  heated  air,  while  in  the  homogen- 
izing process,  the  atomized  spray  is  discharged  into  a  liquid 
medium,  milk. 

The  degree  of  fineness  of  the  atoms  in  either  case  depends 
on  the  speed  with  which  the  liquid  passes  through  the  orifice ; 
the  higher  the  speed  the  finer  and  more  minute  the  atoms.  And 
the  speed  of  passage  in  turn  depends  on  the  degree  of  pressure 
and  the  size  of  the  orifice.  The  greater  the  pressure  and  the 


126 


EVAPORATED  MILK — HOMOGENIZING 


finer  the  opening,  the  faster  the  milk  travels  through  the  orifice; 
and  in  the  case  of  the  homogenizer,  the  finer  the  division  of  the 
fat  globules  in  the  homogenized  milk 

The  tendency  of  fat  globules  to  separate  out  in  homogenized 
evaporated  milk  is  further  reduced  by  the  fact  that  the  homogen- 
izer also  alters  the  physical  condition  of  the  casein,  making  it 
more  viscous  and  thereby  increasing  the  resistance  which  the 
fat  globules  must  overcome  in  their  upward  passage. 

The  exact  changes  which  the  casein  undergoes  are  not  well 
understood,  but  it  is  not  improbable  that  either  the  high  pressure 
or  the  vibration,  or  both,  to  which  the  milk  is  subjected  in  the 
homogenizer,  bring  about  a  molecular  rearrangement  of  the 
casein.  Possibly  these  factors  cause  the  lactic  acid  which  is 
increased  due  to  the  concentration  of  the  evaporated  milk,  to 
remove  calcium  from  the  casein,  leaving  a  part  of  the  casein 
as  free  casein  which  is  a  solid,  and  a  part  of  the  casein  as  casein 
lactate  which  is  in  a  colloidal  state  and  which  is  readily  hy- 
drolized. 

The  fact  remains  that,  when  the  homogenizing  is  done  un- 
der relatively  high  pressure,  or  when  done  in  a  homogenizer 
carrying  a  spring-loaded  valve  which  tends  to  vibrate  or  pound 
the  constititents  of  the  milk,  the  resulting  homogenized  milk 
increases  in  thickness,  is  more  susceptible  to  the  curdling  act- 
ing of  the  heat  in  the  sterilizer  and  is  more  prone  to  "feather" 
or  curdle  when  poured 
into  hot  coffee. 

The  essential  fea- 
tures of  an  efficient  an.d 
reliable  homogenizer 
are :  A  high  class,  high 
pressure,  sanitary  milk 
pump,  a  resistance 
valve  or  similar  homo- 
genizing arrangement 
made  from  material 
which  will  not  wear  nor 
rust,  and  a  means  for 
a  c  c  u  r  ately  adjusting 

Fig-.  47.    The  Gaulin  homogenizer 

this   valve.  Courtesy  of  Creamery  Package  Mfg.  Co. 


EVAPORATED  MILK — HOMOGENIZING 


127 


Kinds  of  Homogenizers. — There  are  at  this  time  three  makes 
of  homogenizers  in  use  in  this  country,  namely,  the  "Gaulin" 
homogenizer,  the  "Progress"  homogenizer  and  the  "Viscolizer." 

In  the  Gaulin  homogenizer,  the  milk  is  forced,  by  means  of 
single-acting  pumps,  against  an  agate  valve  which  presses  against 
a  ground  valve  seat.  The  milk  has  to  pass  between  the  ground 
surfaces  of  this  valve  and  valve  seat. 

In  the  Progress  homogenizer  the  homogenizing  principle 
consists  of  forcing  the  milk,  by  means  of  single  acting  pumps, 
between  a  series  of  discs  with  ground  surfaces.  The  discs  lie 


Fig-.  48.     The  Progress  homog'enizer 
Courtesy  of  Davis-Watkins  Dairymen's  Mfg.  Co. 


Pig".  49. 

Homogenizing-    discs 
and    screw 
mechanism 


flat  one  upon  the  other,  they  are  enclosed  in  a  cylinder  and  are 
held  in  place  by  a  rod  running  through  their  center.  The  discs 
are  pressed  against  each  other  by  a  heavy  spiral  screw,  which 
regulates  the  pressure  to  which  the  milk  is  subjected.  The  milk 
passes  from  the  center  to  the  periphery  of  the  discs.  The  discs 
used  in  this  machine  are  of  two  types.  One  type  has  very  fine 
irregular  grooves.  The  milk  shoots  through  these  grooves 
against  hard  shoulders.  The  other  type  of  discs  has  smooth 
surfaces  but  their  area  of  contact  is  narrow.  The  milk  passes 
through  these  smooth  surfaces, 


128 


EVAPORATED  MILK — HOMOGENIZING 


Tig.  50.     The  Viscolizer 

Courtesy  of  John  W.  Ladd  Co. 


The  Viscolizer. — This  homogenizer  is  equipped  with  a  cone- 
shaped  resistance  valve  of  "Viscolite"  metal,  through  which  the 
milk  is  forced.     The 
conical  valve  has  an 
accurately      fitted 
guide    in    the    valve 
seat,  for  the  purpose 
of     lifting     squarely 
from    the    seat    and 
providing    an    open- 
ing of  equal  dimen- 
sions  for   the   entire 
circumference.     This 
valve  is  regulated  by 
a    differential    screw 
mechanism  in  which 
the  travel  or  advance 
of  this  screw  is  reduced  28  times  from  its  normal  pitch,  making 
possible    a   very   fine    adjustment.      One   complete   turn   of   the 
handwheel  opens  or  closes  the  valve  approximately  to  .001   of 
an  inch.  The  milk  is  forc- 
ed through  this  valve  by 
•a  triple  pressure  pump. 

Operation  of  the  Ho- 
mogenizer.— In  order  to 
avoid  fat  separation  it  is 
necessary  to  subject  the, 
milk  to  enough  pressure 
to  reduce  the  fat  globules 
to  at  least  one-third  their 
original  size.  If  enough 
pressure  is  applied  to  di- 
vide the  fat  globules  into 
much  smaller  units  there 
is  a  tendency  to  also 
change  the  properties  of 

the   casein    tO   SUch   an   ex-  Courtesy   of   Union   Steam   Pump   Co. 

tent  as  to  cause  it  to  give  rise  to  copious  precipitation,  when  the 
evaporated  milk  is  sterilized,  and  making  the  finished  product 


Fig-.  51.     Atomizing-  valve  and  differential 
screw  mechanism   of  Viscolizer 


EVAPORATED  MILK — COOUNG  129 

curdy  and  unmarketable.  In  this  case  the  cure  would  be  more 
disastrous  than  the  original  defect.  Great  care  must,  therefore, 
be  exercised,  guarding  against  the  use  of  excessive  pressure  that 
would  injure  the  casein.  Experiments  have  shown  that  a 
pressure  of  between  one  thousand  and  fifteen  hundred  pounds 
per  square  inch  is  sufficient  to  prevent  fat  separation  and  is 
practically  harmless  as  far  as  its  objectionable  effect  on  the 
casein  in  the  evaporated  milk  is  concerned. 

The  evaporated  milk  is  run  through  the  homogenizer  hot, 
just  as  it  comes  from  the  vacuum  pan  or  standardizing  tank.  If 
the  evaporated  milk  were  homogenized  cold,  the  fat  globules, 
instead  of  being  subdivided  would  unite  into  butter  granules,  the 
milk  would  churn.  The  first  pailful  of  milk  passing  through  the 
machine  should  be  returned  to  the  supply  tank,  as  on  the  start, 
the  pressure  is  not  uniform  and  homogenization  is  incomplete. 

The  pistons,  cylinders,  valves  and  pipes  of  the  homogenizer 
should  be  kept  in  sanitary  condition.  They  are  difficult  to  clean. 
After  homogenizing,  the  machine  should  be  kept  in  operation, 
running  water  through  it,  until  most  of  the  remnants  of  evapo- 
rated milk  are  rinsed  out;  then  hot  water  containing  some 
active  alkali  should  be  pumped  through  ;  this  should  be  followed 
by  clean  hot  water  and  steam.  Unless  this  machine  is  kept 
scrupulously  clean,  it  may  become  a  dangerous  source  of  con- 
tamination, infecting  the  evaporated  milk  with  spore  forms 
that  are  exceedingly  resistant  and  which  are  liable  to  pass  into 
the  finished  product  alive,  in  spite  of  the  sterilizing  process, 
causing  the  goods  to  be  a  complete  loss,  due  to  subsequent 
fermentation. 

CHAPTER  X. 
COOLING. 

In  the  cooling  of  the  evaporated  milk,  no  attention  need  be 
paid  to  sugar  crystallization.  In  this  class  of  goods  there  is 
plenty  of  water  to  keep  the  milk  sugar  in  ready  solution.  The 
evaporated  milk  can,  therefore,  be  cooled  as  rapidly  as  facilities 
permit.  The  cooling  may  be  accomplished  in  similar  ways  as 
are  used  for  cooling  fresh  milk.  From  the  homogenizer  the 
evaporated  milk  is  run  over  a  surface  cooler,  or  cooling  coil.  It 


130 


EVAPORATED  MILK — COOUNG 


is  advisable  to  cover  the  coils  with  a  jacket  of  galvanized  iron, 
tin  or  copper,  so  as  to  avoid  undue  contamination  of  the  milk 
from  dust,  flies,  and  other  undesirable  agents.  In  so~?  oon- 
denseries  trie  hot  evap- 
orated milk  is  forced 
through  double  pipes, 
c'old  water  passing  be- 
tween the  inner  and 
outer  pipes,  or  the  coils 
through  which  the  milk 
passes  are  submerged 
in  a  tank  of  cold  water. 
The  only  objection  to 
this  system  is  that  the 
pipes  are  more  difficult 
to  clean  than  in  the 
case  of  an  open  surface 
cooler.  Where  this  sys- 
tem is  used,  the  pipes 

.  Tig.  52.     Surface  cooler  for  evaporated  milk 

should  be  equipped  Courtegy  of  Davis.Watklns  Dairymen>s  Mfg.  Co. 
with  sanitary  fittings 

so  that  they  can  be  readily  swabbed  out  from  both  ends.  In 
other  factories,  the  evaporated  milk  is  cooled  in  revolving  cans 
with  stationary  paddles,  similar  as  described  and  used  for 
sweetened  condensed  milk,  with  the  exception  that  cold  water 
is  run  into  the  cooling  tank  at  once.  In  still  other  factories  the 
cooling  is  done  in  vats  or  tanks  by  means  of  revolving  coils 
which  carry  the  cooling  medium.  If  the  evaporated  milk  is  not 
homogenized,  it  should  be  cooled  as  soon  as  it  leaves  the  vacu- 
um pan. 

Holding  Tanks. — The  cooling  and  holding  of  evaporated 
milk  may  be  accomplished  in  the  same  series  of  equipment  as 
described  and  illustrated  under  cooling  of  sweetened  condensed 
milk,  Fig.  38.  The  tanks  for  holding  this  product  are  preferably 
jacketed,  so  as  to  make  possible  the  circulation  of  cold  water 
or  brine,  in  case  the  evaporated  milk  must  be  held  for  a  consider- 
able number  of  hours  in  the  holding  tank.  Some  of  these  tanks 
are  equipped  with  propellers  eccentrically  located,  facilitating 


EVAPORATED  MILK — COOLING  131 

the  agitation  of  the  contents  and  bringing  all  parts  of  the  milk 
in  direct  contact  with  the  cooling  surface. 

In  factories  where  these  large  glass-lined  tanks  are  installed, 
each  successive  batch  of  evaporated  milk  is  transferred,  at  the 
conclusion  of  the  process  of  evaporation  and  homogenization,  to 
this  large  holding  and  cooling  tank,  where  all  the  batches  of  the 
same  day's  make  are  cnoled,  mixed  and  held  until  the  last  batch 


Fig1  53.     Holding*  tank  for  evaporated  milk 
Courtesy  of  The  Pfaudler  Co. 

is  in  the  tank.  The  standardization  of  the  evaporated  milk  may 
be  deferred,  until  all  the  batches  of  one  and  the  same  day's  make 
have  reached  the  holding  tank  and  the  entire  mixture  is  then 
standardized  to  the  desired  composition  by  the  addition  of 
distilled  water,  skim  milk,  or  cream,  according  to  needs.  The 
evaporated  milk  in  this  tank  is  usually  cooled  to  and  held  at  40 
to  45  degrees  P.  until  next  morning,  when  the  filling  into  tins 
commences.  See  also  "Standardization,"  Chapter  XXIX. 


132 


EVAPORATED  MILK — 


It  should  be  understood  that,  at  this  stage  of  the  process, 
the  evaporated  milk  is  not  sterile,  nor  does  it  contain  cane  sugar 
to  preserve  it,  neither  is  it  sufficiently  concentrated  to  be  pre- 
served because  of  the  absence  of  moisture.  If  exposed  to  heat, 
such  as  summerheat,  or  even 
room  temperature,  its  acidity 
will  increase  rapidly,  thereby 
rendering  the  subsequent 
sterilizing  process  difficult. 
Therefore,  unless  it  is 
canned  and  sterilized  im- 
mediately after  it  leaves  the 
vacuum  pan,  or  the  homo-, 
genizer  in  case  it  is  homo- 
genized, it  should  be  cooled 
promptly  to  a  temperature 
low  enough  to  check  bac- 
terial development,  40  to  45 

degrees   F.,  or  below.    In  the  courtesy  of  Arthur  Harris  &  Co. 

absence  of  holding  tanks  or 

vats  with  refrigerating  facilities  as  described  above,  the  cooled 
evaporated  milk  may  be  drawn  into  40  quart  milk  cans,  and  set 
in  the  cold  room,  or  these  cans  may  be  submerged  in  a  tank  of 
ice  w'ater. 


Fig-.  54.     Hand  filling*  machine  for  evap- 
orated milk 


FILLING. 

The  cooled  evaporated  milk  is  filled  into  tin  cans  ranging 
in  size  from  eight  ounces  to  one  gallon.  The  gallon  cans  are 
usually  filled  by  hand.  The  filling  of  the  smaller  cans  is  done 
by  automatic  filling  machines. 

Of  late  years  much  progress  has  been  made  in  the  con- 
struction of  different  types  of  filling  machines  for  evaporated 
milk.  The  openings  in  the  cans  through  which  the  cans  are 
filled  range  from  the  Sanitary  can,  which  is  filled  with  the  top 
of  the  can  entirely  removed,  to  the  venthole  can  with  an  opening 
of  not  more  than  one-eighth  inch  in  diameter.  The  filling  ma- 
chines are  constructed  to  fill  by  gravity,  under  pressure,  or  in 
vacuo. 


EVAPORATED  MILK — 


133 


These  filling  ma- 
chines should  be  thor- 
oughly washed  and 
freed  from  all  remnants 
of  evaporated  milk  ad- 
hering to  the  valves 
and  other  parts  after 
each  use.  Remnants  of 
vmilk  left  in  any  part  of 
the  filling  machine  de- 
compose readily  and 
impair  the  wholesome- 
ness  and  marketable 
properties  of  the  prod- 
uct. This  is  an  impor- 
tant point  and  one  too 
often  neglected.  Much 
of  the  spoiled  evap- 
orated milk  may  be  the 
result  of  the  use  of  un- 
sanitary and  unclean 
filling  machines.  The 

fact,  that  the  evaporated   milk  is   sterilized   after  it  leaves  the 
filling  machine,  is  no  excuse  for  unclean  filling  machines.     The 

operator  should  bear  in  mind  that  the 
milk  running  through  an  unclean  filling 
machine  becomes  contaminated  with 
millions  of  bacteria.  The  more  bacteria 
it  contains,  the  more  difficult  it  is  to 
render  it  perfectly  sterile.  Furthermore, 
sporeforms  are  prone  to  develop  in 
the  decaying  remnants  of  milk ;  these 
spores  are  very  resistant  and  require 
excessively  high  sterilizing  tempera- 
tures to  be  destroyed. 

In  the  filling  of  the  venthole  cans 
the    foaming   of    the    evaporated    milk 

rig-.  56.    venthole  can         frequently    causes    serious    annoyance. 
F.  G.  Di?ckreresSoyn "company      This  can  be  avoided  by  having  the  milk 


Fig*.  55.     Venthole  filling*  machine 

Courtesy  of  F.  G.  Dickerson  Company 


134  EVAPORATED  MILK — SEAUNG 

at  the  proper  temperature  at  the  time  of  filling.  Experience  has 
shown  that  warm  milk,  or  milk  with  a  temperature  above  about 
60  degrees  F.  causes  more  trouble  in  this  respect  than  cold 
milk. 

With  the  rapid  and  general  adoption  and  use  among  con- 
denseries  of  a  cold  storage  system,  the  evaporated  milk  usually 
has  a  temperature  between  40  and  50  degrees  F.,  when  it  reaches 
the  filler,  and  at  these  temperatures  the  tendency  to  foam  is 
reduced  to  such  an  extent  that  the  filling  can  be  done  without 
interference  or  interruption  due  to  foam. 

In  order  to  economize  both  space  and  time,  it  has  been 
found  advisable  to  connect  the  pipe  feeding  the  filler  direct  with 
the  holding  tank.  The  extent  of  elevation  of  the  holding  tank 
over  the  filler  obviously  controls  the  gravity  pressure  under 
which  the  evaporated  milk  enters  the  filling  machine.  If  the 
holding  tank  is  located  at  a  high  elevation,  therefore,  the  speed 
of  filling  can  be  materially  increased. 

SEALING. 

The  filled  cans  should  be  capped  and  sealed  at  once.  The 
seal  must  be  hermetical  and  strong  enough  to  withstand  the 
strain  of  the  subsequent  sterilizing  process.  With  the  exception 
of  the  "Sanitary  can,"  seals  without  solder  have  so  far  proven 
unsatisfactory  in  the  canning  of  evaporated  milk.  They  are 
prone  to  weaken  in  the  sterilizer  and  cause  "leakers."  Most  of 
the  cans  on  the  market  containing  evaporated  milk  are,  therefore, 
sealed  with  solder.  Sealing  evaporated  milk  cans  with  solder 
is  by  far  the  safest  method.  For  details  of  methods  of  sealing 
see  Chapter  VII. 

For  the  sealing  or  tipping  of  the  venthole  cans  an  automatic 
tipper  is  usually  attached  to  the  filling  machine,  so  that  when 
the  cans  leave  the  filling  machine,  they  have  also  been  sealed. 

It  is  exceedingly  important  that  the  sealing  be  done  per- 
fectly, because  even  minute  leaks  cause  the  evaporated  niilk  in 
the  cans  to  become  contaminated  causing  spoilage.  In  order  to 
detect  cans  with  imperfect  seals  all  the  cans,  as  they  come  from 
the  filling  and  sealing  machine,  are  carefully  inspected  for  leaks. 
This  may  be  done  by  the  use  of  a  test  bath  consisting  of  a  narrow 


EVAPORATED  MILK — SEALING 


135 


oblong  trough,  filled  with  hot  water  and  through  which  the  cans 
pass  on  an  endless  chain.  In  the  case  of  leaky  cans,  the  heat  of 
the  hot  water  bath  expands  the  air  in  the  cans  and  causes  it  to 
escape  through  the  leak  in  the  seal  and  percolate  upward  in  the 
water  in  the  form  of  air  bubbles.  The  operator  standing  over 
the  test  trough  picks  the  cans  which  expel  air  bubbles  out  so 
that  the  defective  seals  can  be  mended. 

Most  condenseries  manufacturing  evaporated  milk  are  now 
using  a  hot  water 
bath  for  testing  the 
sealed  cans.  But  ex- 
perience has  shown 
that  the  hot  water 
baths  built  on  the 
continuous  chain 
principle  often  fail 
to  give  the  desired 
efficiency.  This  is  not 
the  fault  of  the  ma- 
chine, but  it  is  due 
to  the  fact  that  it 
becomes  very  tiresome  for  the  inspector  to  watch  the  moving 
line  of  cans  in  the  water  bath  and  he  soon  becomes  careless  and 
his  work  inefficient.  It  has  been  found  that  baths  constructed 
and  operated  on  the  principle  of  submerging  a  whole  tray  full 
of  cans,  (usually  24  cans)  at  a  time,  give  more  satisfactory  re- 
sults, relieving  the  monotony  and  preserving  more  successfully 
the  keenness  of  observation  of  the  inspector. 

The  venthole  filler  is  simple  in  construction,  economical  in 
operation  and  easily  cleaned  and  kept  in  sanitary  condition.  The 
milk,  from  the  time  it  comes  within  the  range  of  the  filler,  is  no 
longer  exposed  to  contaminating  influences,  such  as  the  hands 
of  employes,  insects,  etc.  The  cans  are  uniformly  filled  to  within 
one  gram  of  the  guaranteed  weight  and  the  vents  or  pin  holes 
are  automatically  sealed  with  the  minimum  amount  of  solder. 
While  the  quantity  of  solder  must  necessarily  vary  with  oper- 
ating conditions,  it  is  possible  to  limit  the  average  amount  of 
solder,  under  proper  conditions,  to  5  ounces  per  1000  cans.  The 


Fig1.  57.     Chapman  automatic  can  tester 
Courtesy  of  Schaefer  Mfg.   Co. 


136  EVAPORATED  MILK— STERILIZING 

fact  that  the  vent  hole  or  pin  hole  filler  operates  by  gravity,  as 
to  both,  the  empty  cans  and  the  inflowing  evaporated  milk,  re- 
duces the  hitman  and  mechanical  error  to  the  minimum,  once  the 
machine  is  set  for  operation. 

The  acknowledged  advantages  of  the  venthole  filler  have 
made  its  general  adoption  and  use  rapid  and  it  is  estimated  that 
'today  over  90  per  cent  of  the  American  evaporated  milk  is 
being  canned  by  this  type  of  filling  machine. 

CHAPTER  XI. 
STERILIZING. 

The  sealed  cans  are  now  ready  for  the  sterilizer.  If  they 
cannot  be  sterilized  within  an  hour  or  two  they  should  be  sub- 
merged in  ice  water  or  placed  in  a  refrigerating  room  until  the 
sterilizer  is  ready  for  them.  This  precaution  is  especially  ad- 
visable in  summer. 

Purpose  of  Sterilization. — The  chief  purpose  of  subjecting 
the  evaporated  milk  to  the  sterilizing  process  is  to  kill  all  germ 
life  and,  therefore  preserve  the  product  permanently.  When 
the  hermetically  sealed  cans  come  from  the  sealing  room,  their 
contents  are  not  sterile.  The  only  means  to  preserve  this  milk 
is  to  subject  it  to  temperatures  high  enough  to  kill  all  forms 
of  ferments,  organized  and  unorganized,  vegetative  cells  and 
spores.  The  success  of  the  manufacture  of  this  product  depends 
to  a  large  extent  on  the  process  of  sterilization. 

Aside  from  this,  the  manufacturer  aims  to  gain  another  com- 
mercially important  condition,  namely,  to  prevent  the  separation 
of  the  butter  fat.  Before  sterilization,  there  is  nothing  to  prevent 
the  fat  from  separating  out  in  the  evaporated  miilk  and  from 
churning  in  transportation,  unless  the  evaporated  milk  was 
homogenized.  The  sterilizing  process  helps  to  so  change 
the  physical  properties  of  the  milk,  that  this  tendency  of  the 
fat  to  separate  is  greatly  minimized.  The  sterilizing  tem- 
peratures used,  further  lend  to  the  evaporated  milk  a  creamy 
consistency  and  yellowish  color,  giving  the  product  a  semblance 
of  richness. 


EVAPORATED  MILK — STERILIZING 


137 


Pig-.    58. 
Sterilizer  for  evaporated  milk 

Courtesy  of  Arthur  Harris  &  Co. 


Sterilizers.— The  predomi- 
nating apparatus  used  for  ster- 
ilizing is  a  huge,  boiler-like, 
hollow,  iron  cylinder  or  box. 
It  opens  either  at  one  end 
or  on  the  side.  Its  interior 
is  equipped  with  a  revolving 
framework,  steam  inlet  with  a 
perforated  steam  distributing 
pipe  in  the  bottom  of  the  steril- 
izer and  extending  over  the  entire  length  of  the  sterilizer,  a  water 
exhaust,  a  water  inlet  with  a  water  distributing  pipe  in  the 
top  of  the  sterilizer  and  running  the  entire  length  of 
the  sterilizer  and  a  water  exhaust.  The  sterilizer  carries  on  its 
exterior  a  steam  gauge,  a  vacuum  gauge,  a  water  gauge,  a  blow- 
off  valve  and  a  high-temperature  thermometer  (registering  to 
about  280  degrees  F.).  In  some  makes  of  sterilizers  the  interior 
frame-work  does  not  revolve  on  its  axis,  but  moves  back  and 
forth  by  means 
of  a  direct-act- 
ing, steam- 
driven  piston, 
attached  to  the 
back  end  of  the 
sterilizer.  The 
purpose  of 
keeping  the 
cans  in  motion 
while  heat  is 
applied,  is  to 
heat  the  con- 
tents  rapidly 
and  uniformly, 
and  to  prevent 
the  evaporated 
milk  from  bak- 
ing onto  the 

sides     of     the  Fig".  53.     Sterilizer  for  evaporated  milk 

cans          A       Still  Courtesy  of  The  Engineering  Company 


138  EVAPORATED  MILK — STERILIZING 

other  form  of  sterilizer  is  the  continuous  sterilizer  in  which  the 
unsterilized  cans  pass  into  and  the  sterilized  cans  escape  from 
the  heating  chamber  in  continuous  procession. 

Loading  the  Batch-Sterilizer. — The  sealed  tin  cans  are 
placed  in  heavy  iron  trays,  usually  holding  twenty-four  16-ounce 
cans  or  six  1-gallon  cans.  The  loaded  trays  are  slid  and  locked 
into  the  framework  in  the  interior  of  the  sterilizer.  The  sterili- 
zer is  closed  with  heavy  iron  doors  and  the  framework  is  put 
in  motion.  In  some  makes  of  sterilizers  the  interior  consists  of 
a  large  perforated  iron  box  revolving  on  its  axis.  In  this  case 
the  cans  are  simply  piled  into  this  box,  no  trays  being  used. 

Uniform  Distribution  of  Heat. — Where  no  water  is  used  in 
the  sterilizer  during  the  sterilizing  process,  it  is  important  that 
there  be  a  free  air  space  between  every  two  layers  of  cans,  so 
as  to  allow  the  steam  to  circulate  freely  and  to  come  in  direct 
contact  with  every  can.  When  the  cans  are  piled  into  the  ster- 
ilizer six  to  twelve  layers  deep  without  any  free  air  space  be- 
tween layers,  the  cans  in  t'he  center  do  not  receive  as  much  heat 
as  those  at  the  sides,  ends,  top  and  bottom.  This  causes  irreg- 
ular heating  and  imperfect  sterilization. 

A  satisfactory  means  of  insuring  even  distribution  of  heat 
is  to  fill  the  sterilizer  about  one-thirdful  of  water,  so  that,  when 
the  sterilizer  is  in  operation  the  cans  pass  through  this  water, 
with  each  revolution  of  the  frame  work.  Water  distributes  the 
heat  uniformly,  rapidly  and  there  is  no  danger  of  the  formation 
of  air  pockets  between  the  cans.  Since  the  heat  is  applied  by 
steam  under  pressure,  the  temperature  of  the  water  is  equal  to 
that  of  the  steam  in  the  sterilizer.  This  precaution  is  especially 
necessary  in  the  case  of  baby-size  cans  (eight  ounces)  which  are 
usually  piled  in  stacks  more  than  two  deep.  When  sterilizing 
in  the  absence  of  water  there  is  danger  of  lack  of  uniformity  of 
the  amount  of  heat  they  receive.  The  uniform  distribution  of 
the  steam  by  the  perforated  steam  distributing  pipe  in  the  bot- 
tom of  the  sterilizer  is  essential  for  uniform  heating  of  al!  the 
cans.  If  the  perforations  in  this  pipe  become  enlarged  due  to 
wear,  or  in  case  of  an  iron  pipe  due  to  rusting,  or  if  the  cap  at 
the  end  of  the  pipe  happens  to  come  off,  the  heat  distribution 
is  bound  to  lack  uniformity. 


EVAPORATED  MILK — STERILIZING 


139 


It  is  advisable  and  important  to  establish  the  efficiency  of 
heat  distribution  in  the  sterilizer  by  accurate  test.  For  this 
purpose  the  use  of  cans'  equipped  with  automatic  thermometers, 
similar  to  medical  thermometers,  but  registering  sterilizing  tem- 
peratures, may  be  found  practical.  Such  cans  are  placed  in 
different  parts  in  the  cages  of  the  sterilizer  at  the  time  the  ster- 
ilizer is  loaded,  and  at  the  conclusion  of  the  process  these 


m 


Tig.  60. 

Evaporated   milk   can 
with  tell-tale   ther- 
mometer, complete 


Fig.  62. 

Wrench  for  sealing-  and 
opening  can 


Fig.  61. 
Tell-tale  thermometer 

Courtesy  of  Taylor  Instrument  Co. 

thermometers  indicate  the  maximum  temperature  to  which  the 
contents  of  the  respective  cans  were  heated.  Unfortunately 
these  thermometers  are  not  always  accurate  and  often  they  do  not 
function  properly.  Then  again  the  jars  to  which  they  are  sub- 
jected in  the  revolving  cage  and  again  when  the  trays  contain- 
ing these  cans  are  removed  from  the  sterilizer,  frequently  change 
the  position  of  the  mercury  column,  rendering  its  readings  un- 
reliable and  misleading. 

Another  and  very  simple    and  reliable    method    of  testing 


140  EVAPORATED  MILK — STERILIZING 

the  sterilizer  for  heat  distribution  is  to  test  numerous  cans 
from  different  parts  of  the  sterilizer,  after  sterilization,  for  vis- 
cosity by  means  of  the  Mojonnier  viscosimeter  or  similar  device, 
as  described  under  ''Testing  Sample  Cans  for  Viscosity,"  see 
this  chapter,  succeeding  paragraphs. 

Temperature  and  Time  of  Exposure. — When  the  sterilizer 
is  rilled  with  the  cans  and  closed,  the  frame  work  is  set  in  motion 
and  steam  is  turned  into  the  sterilizer.  In  order  to  hasten  the 
heating  and  expel  all  the  air,  the  exhaust  and  safety  should  be 
left  open  until  the  temperature  has  risen  to  212  degrees  F.  This 
temperature  is  usually  reached  in  about  ten  to  fifteen  minutes. 
The  exhaust  and  safety  are  then  closed. 

From  this  point  on,  the  process  must  depend  on  locality, 
season  o'f  year  and  condition,  properties  and  concentration  of  the 
milk.  No  formula  can  be  laid  down  which  can  be  depended  on 
to  give  uniformly  satisfactory  results  under  all  conditions.  Nor 
does  the  proper  sterilization  depend  on  one  particular  formula. 
There  are  numerous  ratios  of  temperature,  time  of  exposure  and 
extent  of  agitation,  which  when  adjusted  to  local  conditions  may 
give  satisfactory  results.  The  temperature  should  be  high  enough 
and  the  duration  of  exposure  long  enough  to  insure  absolute 
sterility  of  the  product  and  to  give  the  milk  sufficient  body  to 
prevent  the  separation  of  the  butter  fat  in  subsequent  storage. 
The  temperature  should  not  be  so  high  nor  the  duration  of  ex- 
posure so  long,  as  to  cause  the  formation  of  a  hard,  unshakable 
curd  and  dark  color. 

Some  processers  use  a  very  short  process  with  high  tem- 
peratures, others  raise  the  heat  gradually  and  not  to  quite  so  high 
a  degree.  The  more  gradual  heating  is  preferable,  as  it  gives 
the  product  a  better  body  and  more  viscosity,  which  is  neces- 
sary to  keep  the  fat  from  separating  in  storage.  The  author's 
judgment  in  this  matter  is,  that  it  is  not  safe  to  raise  the  tem- 
perature to  less  than  230  degrees  F.  and  it  is  advisable  to  heat 
the  milk  to  234  to  236  degrees  F.,  provided  that  the  milk  is  in 
condition  to  stand  this  heat  without  formation  of  too  firm  a 
curd.  Where  the  maximum  temperature  to  which  the  milk  is 
raised  in  the  sterlizer  is  230  degrees  F.  or  thereabout,  the  raise 
of  the  last  ten  degrees  should  occupy  from  thirty-five  to  forty- 


EVAPORATED  MII.K — STERILIZING  141 

five  minutes,  and  this  time  should  be  about  evenly  distributed 
over  the  last  ten  degrees. 

Of  recent  years,  the  practice  of  stopping  the  reel  of  the 
sterilizer,  either  at  intervals  or  when  the  maximum  temperature 
has  been  reached,  has  been  adopted  by  some  of  the  manufactur- 
ers. In  this  case,  the  temperature  usually  is  rapidly  raised  to 
about  240  degrees  F.,  and  after  keeping  the  reel  running  at  this 
temperature  for  a  few  minutes  (about  two  minutes)  the  reel  is 
stopped  and  this  temperature  is  maintained  for  from  15  to  20 
minutes,  with  the  cans  lying  still.  When  the  "hold"  is  com- 
pleted, the  cooling  proceeds  in  the  usual  way.  Some  condens- 
eries  stop  the  reel  for  several  minutes  once  or  twice  when  the 
temperature  has  been  lowered  and  before  it  has  dropped  to  below 
212  degrees  F. 

When  the  stop  process  of  sterilizing  is  used  it  is  advisable 
also  to  superheat  the  evaporated  milk  to  about  210  degrees  F. 
in  the  vacuum  pan;  then  cool  it  to  about  140  degrees  F.  and 
draw  it  into  the  standardizing  vat  where  it  is  standardized  to 
the  desired  point,  then  it  is  homogenized,  filled  and  sterilized. 
The  superheating  can  also  be  done  in  the  standardizing  vat 
instead  in  the  pan,  by  simply  blowing  steam  direct  into  the 
evaporated  milk. 

Mojonnier  Bros.  Co.  recommend  that,  where  the  stop  proc- 
ess is  used,  the  temperature  be  raised  3  degrees  F.  higher  (or 
to  243  degrees  F.),  than  when  the  reel  is  kept  revolving  during 
the  entire  process.  They  further  recommend  that  the  tempera- 
ture be  maintained  at  243  degrees  F.  for  15  minutes,  during 
the  last  seven  minutes  of  which  the  reel  be  stopped.  This 
refers  to  a  "coming-up  time"  (from  190  degrees  F.  to  240  degrees 
F.)  of  10  minutes. 

This  method  of  sterilizing,  by  stopping  the  reel,  has  the 
advantage  of  developing  in  the  cans  a  soft,  custard-like  coagu- 
lum,  giving  the  product  a  very  heavy  consistency  and  making  it 
appear  rich  and  creamy.  It  represents  a  form  of  superheating, 
however,  which  if  not  done  with  great  care,  may  prove  disas- 
trous, causing  the  evaporated  milk  to  spontaneously  thicken  and 
become  cheesy  in  consistency  upon  storage.  Most  batches  of  the 
stop-reel  process  require  shaking. 

In  his  efforts  to  insure  complete  sterility  the  operator  should 


142  EVAPORATED  MILK — STSRIUZING 

understand  that  the  size  of  the  cans  may  influence  the  sterilizing 
efficiency.  It  takes  more  time  and  agitation  to  sterilize  gallon 
cans  than  small  cans.  At  a  time  of  the  year  when  the  milk  con- 
tains micro-organisms  of  relatively  high  resistance  to  heat,  as 
is  often  the  case  especially  in  fall  and  winter,  the  per  cent  loss 
of  gallon  cans  due  to  "swell  heads"  may  become  disastrously 
large,  unless  the  manufacturer  makes  a  special  effort  to  adjust 
his  process  for  gallon  cans.  Gallon  size  cans  require  about  one 
degree  F.  more  heat  on  a  15  minute  run  of  holding  than  tall-size 
cans,  and  tall-size  cans  require  about  one  degree  F.  more  than 
family-  and  baby-size  cans. 

The  installation  and  efficient  use  of  automatic  temperature 
controllers  and  recorders  is  of  material  assistance  for  securing 
uniform  results  of  sterilization.  These  accessories  are  made  use 
of  in  numerous  factories,  and  have  proven  to  be  'of  valuable 
help  to  the  manufacturer.  Aside  from  the  fact  that  they  actu- 
ally do  facilitate  the  temperature  control,  they  automatically 


Fig*.  63.     Bulb  for  automatic  temperature  control 
Courtesy  of  Taylor  Instrument  Co. 

make  for  increased  efficiency  of  the  operator.  The  knowledge 
of  the  operator  that  his  work  is  permanently  recorded  and 
checked  up  exerts  a  beneficial  effect  on  his  performance. 

The  operation  of  an  experimental  or  pilot  sterilizer  also  has 
proven  a  great  help  in  the  accurate  determination  of  the  amount 
of  heat  which  the  evaporated  milk  of  any  batch  requires,  to 
produce  the  desired  viscosity,  body  and  color  and  that  it  will 
stand  without  becoming  hopelessly  curdy.  These  machines  are 
of  small  size,  accommodating  only  a  few  cans. 

A  few  sample  cans  of  each  batch  are  placed  in  the  pilot 
sterilizer  and  run  through  the  process.  Thus  the  proper  process 
to  be  used  for  the  entire  batch  in  the  large  sterilizer  may  be 
adjusted  according  to  the  behavior  of  the  contents  of  the  sample 
cans  in  the  pilot  sterilizer. 

Qualifications  of  the  Processor. — The  operator,  or  the  person 


EVAPORATED  MILK — STERILIZING  143 

directing  the  sterilizing  process,  should  thoroughly  appreciate 
the  complexity  of  the  product,  understand  the  -cause  and  effect 
of  the  many  influencing  factors,  study  the  ever-changing  condi- 
tions and  modify  the  process  in  accordance  with  prevailing  con- 
ditions. He  shpuld  know  that  during  the  exceedingly  hot  sum- 
mer days,  when  the  cows  suffer  from  heat  and  are  pestered  with 
flies,  the  milk  will  not  stand  as  much  heat  without  badly  cur- 
dling in  the  sterilizer  as  under  more  favorable  conditions.  He 
should  know  that  toward  and  during  the  fall  months  the  organ- 


Fig.  64.     Pilot  sterilizer 
Courtesy  of  The  Engineering  Company 

isms  normally  present  in  milk  are  more  resistant  and  require 
higher  heat  to  be  destroyed,  than  earlier  in  the  season. 

Rapid  and  Uniform  Cooling. — As  soon  as  the  required  heat 
has  been  given  the  milk  in  the  sterilizer,  the  steam  should  be 
turned  off  and  the  exhaust  and  drain  should  be  opened.  When 
the  temperature  has  dropped  to  about  220  degrees  F.,  cold  water 
should  be  turned  into  the  sterilizer  while  the  cans  are  constantly 
in  motion,  until  the  cans  are  cool  enough  to  handle.  There 
should  be  enough  cold  water  available  to  reduce  the  tempera- 


144  EVAPORATED  MILK — STERILIZING 

ture  to  70  or  80  degrees  F.  in  twenty  minutes  for  gallons  and  in 
ten  to  fifteen  minutes  for  small  size  cans.  The  water  pipe  should 
be  so  arranged  as  to  distribute  the  water  uniformly  over  the 
entire  length  of  the  sterilizer. 

If  the  process  is  to  be  successful,  the  processer  must  have 
as  nearly  perfect  control  of  the  heat  as  possible.  This  means 
especially,  that  there  must  be  plenty  of  water  available  to  insure 
rapid  cooling  and  the  water  must  be  distributed  over  the  cans 
uniformly.  "Insufficient  water  supply  and  uneven  distribution 
of  the  water  in  the  sterilizer,  means  that  some  of  the  cans  are 
exposed  to  the  sterilizing  heat  longer  than  others,  causing  lack 
of  uniformity  in  the  smoothness  and  color  of  the  milk  of  different 
cans  of  the  same  batch.  Delayed  cooling,  owing  to  insufficient 
water  supply,  has  the  further  disadvantage  of  causing  the  cans 
to  bulge  badly,  owing  to  the  difference  in  pressure  between  the 
interior  and  exterior  of  the  cans.  This  is  especially  noticeable 
in  gallon-size  cans,  the  ends  of  which  may  become  badly  dis- 
torted, present  an  unsightly  appearance  and  their  seams  and 
seals  may  be  weakened  to  the  extent  of  producing  "leakers." 
Excessive  bulging  and  injury  to  the  cans  can  be  avoided  by 
admitting  to  the  sterilizer  a  sufficient  quantity  of  compressed 
air  at  the  conclusion  of  the  sterilizing  process,  to  take  the  place 
of  the  steam  pressure  and  thereby  equalizing  the  pressure  be- 
tween the  outside  and  inside  of  the  cans  during  the  cooling 
process. 

Fractional  Sterilization. — In  the  early  days  of  the  manu- 
facture of  evaporated  milk  the  product  was  sterilized  by  frac- 
tional sterilization.  This  method  has  now  been  largely  aban- 
doned, but  is  occasionally  used  when  the  milk  happens  to  be 
in  very  abnormal  condition.  The  milk  is  heated  in  the  sterilizer 
to  considerably  lower  temperatures  than  those  stated  above,  and 
this  heating  is  repeated  on  two  or  three  successive  days.  The 
principle  of  this  process  is  to  kill  all  vegetative  forms  of  bac- 
teria during  the  first  heating.  This  gives  the  spores  a  chance 
to  develop  into  vegetative  forms  by  the  second  and  third  days, 
which  forms  are  then  destroyed  during  subsequent  heating.  This 
system  of  sterilization  is  not  practical  for  general  use.  It  is  too 
great  a  tax  on  the  capacity  of  the  average  factory  and  increases 


EVAPORATED  MILK — STERILIZING  145 

the  cost  of  manufacture.  It  should,  therefore,  be  made  use  of 
only  in  exceptional  cases,  when  it  is  known  that  a  certain  batch 
of  milk  could  not  be  put  through  the  higher  sterilizing  tempera- 
tures without  causing  the  product  to  become  permanently  curdy. 

Standardization  of  Properties  that  Influence  Behavior  of 
Evaporated  Milk  toward  Heat  of  Sterilization. — In  the  foregoing 
discussion  of  the  sterilizing  process  no  mention  was  made  of 
methods  to  standardize  the  behavior  of  evaporated  milk  toward 
the  sterilizing  heat.  It  was  clearly  pointed  out  that,  in  the 
absence  of  such  methods,  it  is  impossible  to  lay  down  any  one 
formula  for  sterilization  that  would  give  uniformly  satisfactory 
results  under  diverse  conditions  of  the  product  to  be  sterilized. 
The  chemical,  physical  and  physiological  properties  of  milk  are 
ever  changing,  and  even  slight  changes  in  these  properties  often 
cause  wide  variations  in  the  amount  of  heat  the  product  will 
stand  in  the  sterilizer.  This  in  turn  necessitates  constant  changes 
and  modifications  of  the  process,  if  a  marketable  product  is  to 
be  the  result.  Too  much  must  be  left  to  the  judgment  and 
power  of  observation  of  the  processer  and  this  situation  ob- 
viously results  in  excessive  numbers  of  defective  batches  and 
in  costly  losses  and  wastes. 

The  standardization  of  evaporated  milk  for  percentage  of 
fat  and  solids  alone  materially  assists  in  narrowing  down  the 
range  of  variations  in  the  behavior  of  the  milk  in  the  sterilizer, 
but  it  fails  to  adequately  control  those  properties  which  have 
the  greatest  influence  on  the  sensitiveness  of  this  product  toward 
sterilizing  heat.  This  problem  has  confronted  the  manufacturer 
of  evaporated  milk  from  the  very  beginning  of  the  industry. 
Much  experimental  work  has  been  done  in  an  effort  toward  its 
permanent  solution,  but  the  results  have  largely  been  of  local 
and  temporary  success  and  usefulness  only. 

Within  recent  years  the  Mojonnier  Bros.  Co.  of  Chicago 
have  developed  and  have  furnished  the  industry  with  a  simple, 
practical  and  systematic  method  and  suitable  equipment,  for 
controlling  the  properties  of  this  complex  product  with  such 
a  degree  of  accuracy  that  the  adoption  of  a  standard  sterilizing 
formula  has  become  feasible  and  practicable. 


146 


EVAPORATED  MII^K — MOJONNIER  CONTROLLER 


THE  MOJONNIER  METHOD   OF  EVAPORATED   MILK 

CONTROL. 

Principle  of  Method. — This  method  briefly  consists  of  the 
following  outstanding  features : 

1.  The  adoption  of  a  standardized  process  of  sterilization 
designed  and  adapted  for  evaporated  milk  of  superior  quality 


Fig*.  65.     Mojonnier   evaporated  milk  controller 

Courtesy  of  Mojonnier  Bros.  Co. 

for  processing.  This  process  provides  a  very  narrow  range  of 
variation  of  temperature  and  of  time  of  exposure,  in  order  to 
limit  the  personal  factor  with  its  inevitable  uncertainties  to  the 
minimum. 


EVAPORATED  MILK — MOJONNIER  CONTROLLER  147 

2.  A  standard  method  of  determining,  by  means  of  a  pilot 
sterilizer,  a  viscosimeter  and  a  color  test,  the  proper  viscosity 
and  color  that  the  evaporated  milk  should  have  when  it  comes 
from  the  sterilizer;  and 

3.  A  standard  method  of  determining  the  amount  of  bicar- 
bonate of  soda  that  must  be  added  to  any  given  batch  to  evap- 
orated milk  in  case  its  properties  are  such,  that  it  is  unsafe  to 
subject   it,   without   such  treatment,   to   the  temperature   condi- 
tions that  fall  within  the  range  of  the  standardized  process  of 
sterilization. 

Equipment  for  Mojonnier  Method. — The  equipment  designed 
for  this  method  of  evaporated  milk  control,  is  illustrated  in 
Fig.  65,  and  consists  of  the  following  apparatus : 

1.  One  pilot  sterilizer  with  motor,  complete 

2.  2  viscosimeters 

3.  1  venthole  sample  can  filler 

4.  Glassware  for  making  up  and  measuring  sodium  bicarbon- 
ate solution 

5.  1  torsion  balance 

6.  Open-top  cups  and  venthole  tin  cans. 

Preparation  of  I0(/c  Sodium  Bicarbonate  Solution. — The  bi- 
carbonate of  soda  is  used  in  this  test  in  the  form  of  a  10  per 
cent  solution.  This  solution  is  prepared  as  follows: 

1.  Weigh  empty  bottle  to  .01   ounce 

2.  Add  3  ounces  bicarbonate  to  bottle 

3.  Add  27  ounces  warm  water  to  bottle. 

Shake  thoroughly  until  the  bicarbonate  is  all  dissolved. 
Draw  out  as  needed  into  dispensing  bottle,  filling  the  sarnie  not 
over  half  full.  Keep  remainder  tightly  corked  in  the  stock  bottle 
until  needed.  Should  the  bicarbonate  crystallize  out,  prepare 
a  new  lot.  The  above  solution  contains  exactly  10  per  cent 
sodium  bicarbonate. 

Adding  the  Sodium  Bicarbonate  Solution  to  Sample  Cans. — 
Arrange  in  a  row  five  open-top  cups,  marked — X-l-2-3-4  respect- 
ively. These  cups  are  furnished  with  the  Controller.  Cup 
marked  X  is  blank,  to  which  no  bicarbonate  is  added.  To  cup 
marked  No.  1  add  one  charge  of  sodium  bicarbonate  from  the 


148  EVAPORATED  MILK — MOJONNIER  CONTROLLER 

dispensing  burette.  This  is  the  amount  contained  between  the 
upper  two  graduations  on  the  burett'e.  To  cup  marked  No.  2 
add  two  charges,  to  cup  No.  3  add  three  charges,  to  cup  No.  4 
add  four  charges.  Dispensing  burette  furnished  with  the  con- 
troller indicates  how  the  above  quantities  are  to  be  added ;  the 
burette  is  graduated  into  four  separate  charges.  The  unit  with 
one  single  charge  contains  the  equivalent  of  one  ounce  of  sodium 
bicarbonate,  to  one  thousand  pounds  of  evaporated  milk.  Each 
successive  charge  is  a  multiple  of  this  unit.  In  dispensing  the 
bicarbonate  solution,  it  is  best  not  to  fill  the  bottle  more  than 
half  full.  When  filling  the  burette,  the  solution  should  be 
allowed  to  flow  into  it  slowly  in  order  not  to  trap  in  the  air.  If 
air  is  trapped  into  the  burette,  it  is  difficult  to  remove  it,  and 
in  such  a  case  it  is  best  to  run  out  whatever  solution  may  be  in 
the  burette  and  to  put  in  a  new  supply. 

Whenever  the  quality  of  the  milk  is  very  abnormal,  it  may 
be  necessary  to  add  more  than  above  indicated  number  of 
charges  of  bicarbonate  solution  to  the  sample  cans.  In  such 
cases  any  multiples  of  the  above  number  of  charges  may  be 
added.  The  ratio  of  ounces  of  bicarbonate  to  one  thousand 
pounds  of  milk  will  remain  the  same,  being  increased  simply  by 
the  number  of  charges  added  to  each  sample  can. 

Preparation  of  the  Five  Sample  Cans  for  the  Sterilizer.— 
After  the  five  open-top  cups  have  been  treated  with  bicarbonate 
as  indicated  in  the  preceding  section,  they  are  transferred  to  the 
Torsion  Balance  and  exactly  six  ounces  of  milk  is  weighed  into 
each  cup.  This  can  be  done  by  taring  the  entire  set  of  empty 
cups,  and  then  weighing  six  ounces  of  evaporated  milk  into  each 
separate  cup. 

One  set  of  five  empty  cans  is  now  marked  in  the  same  man- 
ner as  the  cups  to  which  the  bicarbonate  solution  was  added, 
namely  as  follows :  X  — .  can  containing  no  bicarbonate ;  1  =  can 
containing  equivalent  of  one  ounce  bicarbonate  per  thousand 
pounds  of  evaporated  milk;  2  =  can  containing  equivalent  of 
two  ounces  per  one  thousand  pounds  of  evaporated  milk ;  3  = 
c#n  containing  equivalent  of  three  ounces  per  one  thousand 
pounds  of  evaporated  milk,  and  4  =  can  containing  equivalent  of 
four  ounces  per  one  thousand  pounds  of  evaporated  milk. 

Next  the  contents  of  the  five  open-top  cups  are  transferred 


EVAPORATED  MILK — MOJONNIER  CONTROLLER 


149 


to  the  five  tin  cans  in  the  order  above  indicated  This  is  done 
by  placing  the  cans  in  pairs,  under  the  two-can  venthole  filler, 
furnished  with  the  Controller,  and  the  cups  with  the  milk  and 
bicarbonate  marked  corresponding  to  the  empty  cans,  are  now 
emptied  into  *the  filler.  Care  must  be  taken  to  keep  the  cans 
in  the  proper  order. 

After  filling,  the  cans  are  tipped,  using  preferably  rosin 
solder.  Should  none  of  this  solder  be  available,  then  great  care 
must  be  exercised  not  to  let  any  of  the  flux  from  the  zinc  chloride 
solder  enter  the  cans.  Zinc  chloride  flux  has  a  very  bad  effect 
upon  the  milk,  and  will  completely  change  the  results. 

Sterilizing  the  Five  Sample  Cans. — The  five  samlple  cans, 
prepared  as  above  directed,  are  now  ready  for  the  sterilizer. 
Place  these  in  the  cage  and  fasten  the  lid  securely,  and  also  turn 
down  the  screws  in  order  to  hold  all  of  the  cans  securely  into 
place.  Adjust  the  cage  in  the  sterilizer  by  means  of  the  thumb 
screw  on  the  right  hand  side,  in  order  to  keep  them  from  having 
end  play.  Close  the  sterilizer  door  securely  so  that  no  steam 
escapes  during  the  sterilizing  process. 

Be  sure  to  provide  circulation  of  the  steam  through  the 
vent  on  the  pipe  surrounding  the  thermometer.  This  little  vent 
should  be  kept  open  during  the  entire  sterilization  operation. 
Fill  the  small  pilot  sterilizer  with  water  to  a  point  half  way 
upon  the  gauge  glass.  Be  sure  to  turn  on  the  switch  to  start 
the  motor  in  operation.  Open  the  "steam  start  valve"  and  take 
five  minutes  to  let  the  heat  reach  190  degrees  F.  or  3  on  the  ster- 
ilizer scale.  Then  let  the  heat  come  up  gradually  from  190  de- 
grees to  240  degrees  F.  or  from  3  to  8  on  the  thermometer,  taking 
one  minute  for  each  5  degrees  as  indicated  in  the  following  table : 


Actual  Temperature 

Actual   Reading 

Point  at  which  Mercury 

in 

upon 

should  be  at  any  given 

Fahrenheit  Degrees 

Thermometer  Scale 

time  coming  up 

240° 

8  points 

20  minutes 

230° 

7  points 

18  minutes 

220° 

6  points 

16  minutes 

210° 

5  points 

14  minutes 

200° 

4  points 

12  minutes 

190° 

3  points 

10  minutes 

150  EVAPORATED  MILK — MOJONNIER  CONTROLLER 

Where  sterilizing  is  done  with  steam  only,  without  using 
superheated  water,  it  is  recommended  to  take  twenty  minutes 
for  coming  up.  The  above  table  is  arranged  upon  this  basis. 
The  table,  however,  can  be  readily  adapted  to  a  system  requir- 
ing fifteen  minutes  for  coming  up,  by  taking  five  minutes  to 
come  up  to  the  point  marked  10  upon  the  table,  or  to  190  de- 
grees F. 

It  is  also  recommended  that  in  the  pilot  sterilizer,  the  sam- 
ples be  cooked  to  243  degrees  F.  and  that  the  "jump"  from  230 
degrees  to  243  degrees  be  made  in  two  minutes.  It  is  very 
important  to  know  the  exact  second  when  the  mercury  column 
reaches  243  degrees.  The  milk  should  be  held  at  this  tempera- 
ture for  fifteen  minutes  to  the  exact  second.- 

Cooling  the  Five  Sample  Cans. — The  instant  the  clock  shows 
that  the  samples  have  been  sterilized  as  indicated  above,  both, 
discharge  valve  and'  cold  water  valve  should  be  opened  simul- 
taneously. It  is  best  to  cool  the  five  samples  to  about  75  de- 
grees F.  This  should  take  not  to  exceed  five  minutes,  depending 
upon  the  temperature  of  the  water  available.  This. is  something 
each  operator  must  judge  for  himself. 

Testing  the  Sample  Cans  for  Viscosity. — As  soon  as  the 
sample  cans  are  cooled  in  the  sterilizer,  as  indicated  above, 
the  cans  are  dried  on  the  outside  and  are  then  opened  and 
each  can  is  placed  in  the  proper  position  in  the  viscosimeter 
rack.  It  will  be  noticed  that  th,e  same  scheme  of  marking  the 
spaces  upon  the  viscosimeter  rack  has  been  observed  as  in  the 
case  of  marking  the  cans.  It  is  very  desirable  to  cool  the  sam- 
ples to  as  nearly  75  degrees  as  possible.  If  this  is  not  done, 
the  viscosity  should  be  corrected  for  temperature,  using  the 
scale  of  corrections  that  is  furnished  with  the  viscosimeters. 
Make  the  viscosity  test  as  follows : 

(a)  Different  sizes  of  balls  are  furnished,  corresponding  to 
the  product  that  it  may  be  desired  to  test  for  viscosity.    A  special 
viscosity  ball  is  furnished  in  the  case  of  evaporated  milk,  and 
this  is  not  interchangeable  with  any  other  ball  for  this  purpose. 
Therefore,  see  that  the  proper  ball  is  being  used. 

(b)  Fasten  one  end  of  the  wire  in  the  knurled  nut  upon  the 


EVAPORATED  MILK — MOJONNIER  CONTROLLER  151 

top  of  the  bent  support,  and  the  other  end  in  the  dial.     Adjust 

the  vertical  position  of 

the   dial   by   raising  or 

lowering,   until   the 

small  lug  on  the  bottom 

of    the    dial    is    in    the 

proper    position    to 

engage    the    trip    upon 

the   right-hand    side   of 

the  stand. 

(c)  Adjust  the  hor- 
izontal  position  of  the 
dial   until  zero  degrees 
is    in    a    line    with    the 
pointer  upon  the  front 
of  the  frame  when  the 
dial  is  balanced  in  -the 
air.     Center  the  dial  in 
the      open      circle      by 
means  of  the  adjusting 
screws    on     the    under 
side  of  the  frame.  Make 
a  test  for  viscosity  di- 
rectly in  the  baby-size 
cans.      Properly   center 
the  can  by  means  of  the 
automatic  arrangement 
provided   for   that  pur- 
pose.    As    already    in- 
dicated,     be      sure      to  Piff.  ^     Mojonnler  vlacoBimeter 
(vatch    the    temperature  Courtesy  of  Mojonnier  Bros.  Co. 
factor  very  closely. 

(d)  Lower  the  ball  into  the  can  of  milk;  turn  the  dial  clock- 
wise one  revolution ;  stopping  when  zero  degrees  upon  the  dial 
is  in  line  with  the  pointer  upon  the  front  of  the  frame.     Hold 
the  dial  in  place  by  means  of  the  lug  and  trip.     When  ready, 
sharply,  release  the  trip,  note  the  degree  where  the  dial  stops, 
just  before  it  starts   upon  the  return   round.     This  will  occur 


152 


EVAPORATED  MILK — MOJONNIER  CONTROLLER 


after  the  dial  has  made  one 
complete,  and  part  of  the 

second  revolution.  The  de- 
gree at  which  the  dial  stops 
will  represent  the  viscosity 
of  the  sample.  The  greater 
the  viscosity,  the  larger  the 
degree  reading  will  be. 

Record  the  viscosity  of 
each  of  the  sample  cans 
tested,  as  indicated  above.' 
Further  instructions  will  fol- 
low as  to  the  method  of  ap- 

,     .  . 

plylr»g  the  information  thus 

obtained. 

Table  for  Correcting  Viscosity  of  Evaporated  Milk  to  75°   F.1 


"READING  CAN  BE  TAKLN 
:LEASED,  I  DIRECT  AT  POINTER,  i 
DIAL  REVOLVES  IN  I  GLASS  OVER  POINT 

THIS  DIRECTION.       ACCURACY. 

Tig.    67. 

Mojoniiier-Doolittle    viscosimeter    dial, 
graduated  to  360° 

Courtesy  of  Mojonnier  Bros.  Co. 


STERILIZING  ROOM 

PACKING  ROOM 

Take 

Add 

Add 

Take 

Add 

Add 

Temp 
Deg. 

off 
Deg. 

Temp. 
Deg. 

on 
Deg. 

Temp. 
Deg. 

on 
Deg. 

Temp. 
Deg. 

off 
Deg. 

Temp. 
Deg. 

on 
Deg. 

Temp. 
Deg. 

on 
Deg. 

F. 

R.2 

F. 

R. 

F. 

R. 

F. 

R. 

F. 

R. 

F. 

R. 

65 

25 

76 

2 

89 

24 

60 

15 

75 

0 

88 

10.0 

66 

22 

77 

4 

90 

25 

61 

14 

76 

1 

89 

10.5 

67 

19 

78 

6 

91 

26 

62 

13 

77 

2 

90 

11.0 

68 

16 

79 

8 

92 

27 

63 

12 

78 

3 

91 

11.5 

69 

13 

80 

10 

93 

28 

64 

11 

79 

4 

92 

12.0 

70 

10 

81 

12 

94 

29 

65 

10 

80 

5 

93 

12.5 

71 

8 

82 

14 

95 

30 

66 

9 

81 

6 

94 

13.0 

72 

6 

83 

16 

96 

31 

67 

8 

82 

7 

95 

13.3 

73 

4 

84 

18 

97 

32 

68 

7 

83 

7.5 

96 

13.6 

74 

2 

85 

20 

98 

33 

69 

6 

84 

8.0 

97 

13.9 

75 

0 

86 

21 

99 

34 

70 

5 

85 

8.5 

98 

14.2 

87 

22 

100 

35 

71 

4 

86 

9.0 

99 

14.5 

88 

23 

72 

3 

87 

9.5 

100 

14.8 

73 

2 

74 

1 

Importance  of  Proper  Viscosity. — The  viscosity  of  evapo- 
rated milk  determines  the  body  and  permanency  of  the  emulsion 
of  the  fat  and  other  solid  and  liquid  constituents  of  the  product 
and  it  further  determines  the  extent  to  which  the  evaporated 


1  Courtesy   of  Mojonnier  Bros.   Co. 

2  R  means  degree  retardation  or  viscosity. 


EVAPORATED  MILK — MOJONNIER  CONTROLLER  153 

milk  may  be  expected  to  withstand  the  sterilizing  heat  without 
danger  of  curdling  in  a  manner  that  would  render  the  product 
unmarketable. 

The  purpose  of  the  viscosity  test,  of  sample  cans  having 
passed  through  the  pilot  sterlizer  or  controller  is,  to 'determine 
whether  the  evaporated  milk  of  the  entire  batch,  without  treat- 
ment will  safely  pass  through  the  adopted,  standard  sterilizing 
process,  or  to  what  extent  this  process  must  be  modified,  or  to 
what  extent  the  product,  before  sterilization  must  be  treated 
with  bicarbonate  of  soda  to  secure  a  good  body,  and  at  the  same 
time  insure  freedom  from  the  formation  of  a  permanent  curd 
when  applying  the  standard  sterilizing  process. 

A  certain  degree  of  viscosity  in  evaporated  milk  is  desirable 
and  necessary  in  order  to  give  the  product  a  .good  body  and  to 
prevent  the  separation  of  the  butter  fat.  . 

But.  as  the  viscosity  increases  a  point  is  reached  beyond 
which  it  is  not  safe  to  go,  because  of  the  danger  of  the  formation- 
of  a  permanent  curd  that  renders  the  product  unmarketable. 

The  increasing  viscosity  is  due  to  a  change  in  the  physical 
properties  of  the  protein  constituents  of  evaporated  milk  result- 
ing from  the  action  of  heat.  The  earlier  stages  of  these  changes 
are  desirable,  because  they  result  in  a  product  of  good  body  and 
of  increased  stability  of  emulsion.  An  excessive  continuation 
of  these  changes  precipitates  the  proteins  in  the  form  of  visible 
particles  of  curd  which,  if  permanent,  spoil  the  product  for  the 
market. 

Factors  which  Influence  the  Viscosity  and  their  Correlation 
to  the  Sterilizing  Process. — The  extent  to  which  heat  increases 
the  viscosity  of  evaporated  milk  is  dependent  on  many  and  vary- 
ing conditions,  such  as  acid  of  milk,  natural  stability  of  proteins 
in  milk  as  related  to  their  behavior  toward  heat,  degree  of  con- 
centration of  evaporated  milk,  degree  of  heat  applied  in  fore- 
warmer,  amount  of  extraneous  water  in  evaporated  milk,  degree 
of  heat  in  the  sterilizer,  duration  of  exposure  to  sterilizing  heat. 
The  resistance  of  the  proteins  to  heat,  as  affected  by  these  sev- 
eral conditions  and  factors,  can  be  modified  and  largely  con- 
trolled if  necessary,  by  the  treatment  of  milk  that  has  an  ab- 
normally low  resistance  to  heat,  with  definite,  small  quantities 
of  bicarbonate  of  soda. 


154  EVAPORATED  MILK — MOJONNIER  CONTROLLER 

The  viscosity  test  therefore  furnishes  a  measure  of  the 
resistance  of  any  given  batch  of  evaporated  milk  toward  steril- 
izing heat.  But  in  order  to  enable  the  operator  to  correctly 
interpret  the  results  of  this  test  and  to  correctly  govern  his 
method  o'f  handling  the  evaporated  milk  according  to  these 
findings,  he  should  have  a  clear  understanding  of  the  correlation 
of  the  several  factors  that  influence  this  resistance  to  heat  and 
that  affect  the  viscosity.  • 

With  reference  to  the  direction  (increase  or  decrease  of 
viscosity)  in  which  these  several  factors  influence  the  viscosity 
and  the  tendency  to  curdle  the  evaporated  milk,  the  following 
general  facts  should  be  known : 

Factors  that        Cl.  high  per  cent  acid  in  milk 

increase  the  vis-        2.  low  stability  of  proteins 

cosity  and  the     J  3.  high  concentration  of  evaporated  milk 

tendency  to  curdle^   4.  high   sterilizing  temperature 

the   milk  j   5.  long  exposure  to  sterilizing  temperature 

6.  high  pressure  in  homogenizer 

1.  low  acidity  in  milk 

2.  great  stability  of  proteins 


Factors  that 
decrease  the  vis- 
cosity and  the    - 
tendencv  to  curdle 


3.  low  concentration  of  evaporated  milk 

4.  low  sterilizing  temperature 

5.  short  exposure  to  sterilizing  heat 

6.  high  temperature  in  forewarmer 

7.  extraneous  water  in  evaporated  milk 

8.  low  pressure  in  homogenizer 
^9.  addition  of  bicarbonate  of  soda 

The  exact  quantitative  relation  of  most  of  these  factors  to 
one  another  and  to  the  viscosity  of  the  evaporated  milk  has  been 
experimentally  determined  by  Mojonnier  Bros.  Co.  for  evapo- 
rated milk  standardized  to  7.8  per  cent  fat  and  25.5  per  cent 
total  solids  as  follows: 

A  40  degree  retardation  or  viscosity  'as  determined  by  the 
Mojonnier  viscosimeter  corresponds  to: 

1.  One  degree  F.  in  sterilizing  temperature  at  the  holding 
point  of  240  degrees  F.,  when  held  for  15  minutes  and  with  the 
same  "coming-up"  time  as  given  under  "Sterilizing  the  Five 
Sample  Cans."  This  means  that  each  degree  F.  above  240  de- 


EVAPORATED  MILK — MOJONNIER  CONTROLLER  155 

grees  F.  under  above  conditions  of  holding  increases  the  retarda- 
tion or  viscosity  40  degrees. 

2.  One  minute  of  time  at  holding  temperature  of  240  de- 
grees F.    This  means  that  each  minute  of  holding  at  240  degrees 
F.  longer  than  15  minutes  increases  the  retardation  or  viscosity 
40  degrees  and  each  minute  of  holding  at  240  degrees  F.  less 
than  15  minutes  decreases  the  retardation  or  viscosity  40  degrees. 

3.  Two  degrees  F.  on  temperature  to  which  milk  is  heated 
in  hot  well  under  212  degrees  F.     This  means  that  for  every 
two  degrees  F.  below  212  degrees  F.  in  the  hot  well  the  retar- 
dation or  viscosity  is  increased  40  degrees'. 

4.  20  pounds  of  extraneous  water  per  1000  pounds  of  evap- 
orated  milk.     This  means  that  the   addition  to  or  presence  in 
evaporated  milk  of  20  pounds  of  extraneous  water  per  1000  pounds 
of    evaporated    milk    reduces    the    retardation    or    viscosity    40 
degrees. 

5.  One  ounce  of  solid  sodium  bicarbonate  per  1000  pounds 
of  evaporated  milk.    This  means  that  the  addition  to  the  unster- 
ilized    evaporated   milk   of   one    ounce    of   bicarbonate    of   soda 
per  1000  pounds  of  evaporated  milk  reduces  the  retardation  or 
viscosity  40  degrees. 

6.  When  using  the  above  correlation  of  factors  as  a  guide, 
it   should   be   borne  in   mind   that,   with   evaporated   milk   of  a 
higher   degree   of   concentration   the   influence   of  these   several 
factors  on  the  retardation  or  viscosity  is  altered  and  intensified. 

The  Correct  Viscosity  for  Evaporated  Milk. — The  experi- 
mental study  of  the  viscosity  of  evaporated  milk  by  Mojonnier 
Bros.  Co.  has  further  demonstrated  that  a  considerable  portion 
of  the  viscosity,  as  determined  immediately  after  the  evaporated 
milk  comes  from  the  sterilizer,  is  lost  during-  the  handling  to 
which  the  product  is  subjected  from  the  time  it  leaves  the  ster- 
ilizer and  until  it  is  ready  to  leave  the  shipping  department, 
and  again  in  transport  until  it  reaches  the  consumer.  Also  the 
extent  of  this  loss  of  viscosity  is  governed  somewhat  by  the  tem- 
perature of  the  milk  while  it  is  so  handled ;  the  higher  the  tem- 
perature the  greater  the  sacrifice  in  viscosity. 

Accordingly  it  has  been  found  that  for  domestic  trade  a 
retardation  or  viscosity  of  150  degrees  is  the  correct  viscosity 
for  evaporated  milk  just  as  it  comes  from  the  sterilizer.  For 


156  EVAPORATED  MILK — MOJONNIER  CONTROLLER 

export  purposes  the  viscosity  should  be  higher,  around  200 
degrees. 

A  150  degrees  viscosity  of  evaporated  milk  immediately 
after  sterilization  is  equivalent  to  a  viscosit3r  of  from  about 
80  degrees  to  100  degrees  by  the  time  the  milk  is  ready  to  leave 
the  shipping  department,  and  this  represents  about  the  correct 
viscosity  for  the  summer  months.  For  the  winter  months  the 
viscosity  should  not  exceed  about  80  degrees  retardation.  Ex- 
cessive viscosity  invites  the  "feathering"  or  curdling  of  the  evap- 
orated milk  when  used  in  hot  coffee  or  when  diluted  with  hot 
water. 

Adding  Sodium  Bicarbonate  to  Batch  of  Evaporated  Milk. — 
As  soon  as  the  controller  and  viscosimeter  tests  are  completed, 
the  batch  of  evaporated  milk  is  ready  to  be  filled  into  the  tin 
cans.  In  case  it  is  necessary  to  add  sodium  bicarbonate,  the 
following  procedure  is  recommended : 

For  convenience  sake  we  will  assume  that  can  No.  2  in 
the  test  showed  the  correct  viscosity,  as  represented  by  a  retar- 
dation of  150  degrees.  To  this  can  had  been  added  sodium 
bicarbonate  on  the  basis  of  two  ounces  per  1,000  pounds  of  milk. 
The  entire  batch  of  milk  containing  24,000  pounds  evaporated 

24,000  X  2 
milk,  hence i~rjnn ~  ^  ounces  of  solid  sodium  bicarbonate 

are  carefully  weighed  out.  This  amount  of  bicarbonate  is  con- 
veniently placed  into  a  10-gallon  milk  can,  a  small  amount  of 
water  is  added  and  preferably  also  a  small  amount  of  evapo- 
rated milk.  This  mixture  is  then  heated  to  a  vigorous  boil, 
which  can  easily  be  done  by  means  of  the  steam  hose.  The 
boiling  should  be  continued  until  the  greater  part  of  the  gas 
generated  has  been  expelled. 

The  hot  mixture  is  now  added  to  the  entire  batch  of  evapo- 
rated milk  in  the  holding  tank.  It  should  be  added  slowly  and 
the  evaporated  milk  should  be  kept  thoroughly  agitated,  not 
only  while  the  bicarbonate  is  added  but  for  from  10  to  20  min- 
utes after  its  addition. 

Adjusting  Sterilizing  Process  to  Different  Sizes  of  Cans. — 

As  stated  elsewhere  in  this  chapter,  different  sizes  of  cans 
require  different  sterilizing  formulas  to  insure  complete  steriliza- 
tion, and  a  similar  effect  has  been  found  also  with  reference  to 


EVAPORATED  MILK — MOJONNIER  CONTROLLER  157 

viscosity.  Thus,  tall  size  cans  require  one  degree  more  heat 
on  a  15  minute  run  of  holding-  than  the  baby  size  cans.  Hence 
if  the  record  for  a* baby  size  batch  of  evaporated  milk  calls  for 
15  minutes  at  240  degrees  F.,  for  tall  size  cans,  the  same  batch 
would  have  to  be  held  for  15  minutes  at  241  degrees  F. 

Irregularities  in  the  Reaction  and  Results  of  Sodium  Bi- 
carbonate.— Generally  speaking  the  Mojonnier  formula  above 
given  for  the  use  of  Bicarbonate  of  Soda  yields  reliable  results 
There  are  occasionally  conditions,  however,  when  the  evaporated 
milk  fails  to  react  normally  with  this  ingredient  and  may  yield 
results  exactly  opposite  those  anticipated.  Instead  of  reducing 
the  viscosity  of  the  milk,  it  increases  the  viscosity.  Abnormal 
cases  of  this  type  suggest  that  the  physical  and  possibly  the 
chemical  make-up  of  the  casein  may  have  undergone  material, 
though  not  as  yet  well  understood  changes. 

Such  abnormal  conditions  may  be  the  result  of  improper 
forewarming  of  the  milk,  the  use  of  excessive  pressure  in  the 
homogenizer,  excessive  heat  in  the  sterilizer,  mixture  of  brirfe 
with  the  evaporated  milk  due  to  leaky  coils  in  the  cooler,  or 
unbalanced  relation  of  the  protein  and  ash  constituents  of  the 
original  milk.  See  also  Chapter  XXIII,  " Defective  Evaporated 
Milk"  under  " Lumps  of  Curd  in  Evaporated  Milk." 

Should  Bicarbonate  of  Soda  or  any  other  Chemical  be  Used 
at  all? — The  foregoing  directions  for  the  use  of  the  Mojonnier 
Controller  and  Viscosimeter  should  not  be  interpreted  to  mean, 
that  this  volume  advocates  the  use  of  bicarbonate  of  soda  in 
the  manufacture  of  evaporated  milk.  In  fact  the  availability 
of  this  equipment  and  of  these  tests  materially  facilitates  the 
manufacture  of  evaporated  milk  without  the  use  of  sodium 
bicarbonate. 

It  is  important  to  realize,  however,  that  the  use  of  sodium 
bicarbonate  for  the  purpose  of  facilitating  the  process  of  ster- 
ilization has  been  pretty  general  for  many  years  prior  to  the 
introduction  of  Mojonnier  equipment  and  methods.  It  has  be- 
come a  fairly  well  established  practice,  accepted  by  the  industry. 
Its  abuse  cannot  be  too  strongly  condemned  and  its  promis- 
cuous use  in  the  absence  of  a  systematic,  scientifically  controlled, 
correct  method,  is  prone  to  invite  its  abuse. 


158  EVAPORATED  MILK — MOJONNIER  CONTROLLER 

While,  in  principle,  the  use  of  bicarbonate  of  soda  in  a 
product  such  as  evaporated  milk  cannot  be  unconditionally 
recommended,  its  proper  and  correct  use,  where  necessary,  has 
proven  a  decided  benefit  to  the  industry,  reducing  the  occurrence 
of  unmarketable  though  otherwise  perfectly  good  batches  of 
evaporated  milk  to  the  minimum,  and  thereby  avoiding  unnec- 
essary economic  loss.  It  is  a  matter  of  choosing  the  lesser  of 
two  evils. 

Irregularities  in  the  behavior  of  evaporated  milk  toward 
the  sterilizing  process,  that  render  the  product  unmarketable  are 
largely  due  to  changes  and  differences  in  the  chemical  compo- 
sition and  physical  and  physiological  properties  of  the  milk. 
Some  of  these  changes  are  under  the  control  of  the  milk  pro- 
ducer on  the  farm,  others  are  under  the  control  of  the  manufac- 
turer and  still  others  are  uncontrollable. 

The  conditions  which  can  and  should  be  controlled  by  the 
producer  refer  largely  to  sanitation  in  the  production  and  care 
of  milk,  prompt  and  proper  cooling,  frequency  of  delivery,  pro- 
tection against  heat  in  transit,  health  of  cows  and  rejection  of 
colostrum  milk.  The  condensery  must  insist  on  cleanly  pro- 
duction, on  proper  cooling  of  the  milk  on  the  farm,  on  daily 
delivery  at  the  factory  (some  condenseries,  especially  those  in 
Europe  receive  their  patrons'  milk  twice  daily),  on  the  proper 
temperature  of  the  milk  upon  arrival  at  the  factory,  on  the  proper 
disposition  of  milk  from  sick  cows  and  of  milk  too  close  before 
parturition,  and  too  soon  after  calving.  Much  of  this  can  be 
accomplished  by  a  rigid  system  of  milk  inspection  on  the  plat- 
form and  frequent  visits  by  the  inspector  to  the  patrons'  farms. 
In  the  case  of  rail  shipments  the  milk  often  is  in  transit  too 
long  to  arrive  at  the  factory  in  the  best  condition. 

The  factors  under  control  of  the  factory,  which  influence 
the  behavior  of  the  evaporated  milk  toward  sterilizing  heat,  refer 
to  sanitation  in  all  departments  where  milk  is  handled  in  the 
plant  and  to  uses  or  abuses  of  the  milk  in  manufacture.  All 
equipment  with  which  milk  comes  in  contact  must  be  kept  in  a 
perfect  state  of  cleanliness  as  outlined  earlier  in  this  volume 
under  "Factory  Sanitation."  The  handling  of  two  days'  milk 
must-  be  discontinued,  the  evaporated  milk  must  not  be  held 
excessively  long  in  the  storage  tanks,  and  if  held  at  all,  it  must 


EVAPORATED  MILK-^  SHAKING  159 

be  cooled  to  a  low  temperature.  All  abuses  of  milk  along  these 
and  similar  lines  are  bound  to  cause  trouble  in  the  sterilizer, 
which  is  avoidable  and  unnecessary. 

Finally  there  are  factors  which  are  not  under  control  but 
which'  also  exert  a  very  marked  influence  on  the  behavior  of 
the  product  toward  sterilizing  heat  at  times.  These  are  invari- 
ably associated  with  changes  in  the  period  of  lactation,  changes 
in  feed  and  climatic  conditions  and  their  effect  on  the  amount  and 
proportion  of  the  protein  .and  ash  constituents  of  milk,  as  ex- 
plained in  Chapter  XXIII,  "Defective  Evaporated  Milk,  Lumps 
of  Curd."  These  conditions  are  not  only  not  controllable,  but 
their  effect  on  the  milk  is  not  determinable  by  any  now  known 
practical  method  of  analyses. 

Proper  attention  to  the  controllable  conditions  will  go  far 
in  making  unnecessary  the  use  of  bicarbonate  in  evaporated 
milk  and  will  at  least  confine  its  use,  when  necessary,  to  very 
small  amounts.  When  these  conditions  have  been  conscientiously 
taken  care  of  and,  in  spite  of  these  precautions,  certain  batches  of 
milk,  because  of  the  above  named  effect  of  uncontrollable  fac- 
tors, require  the  use  of  bicarbonate  in  order  to  insure  safe  ster- 
ilization and  to  avoid  loss,  then  the  emergency  justifies  and 
sound  judgment  and  business  efficiency  demand  recourse  to 
methods  that  the  helping  hand  of  science  has  made  available, 
so  long  as  these  methods  do  not  impair  the  wholesomeness  and 
food  value  of  the  product,  although  their  ethics,  in  principle  at 
least,  cannot  be  approved  for  general  practice.  See  also  /'Effect 
of  Relation  of  Mineral  Constituents  of  Milk,"  Chapter  XXIII, 
"Defective  Evaporated  Milk." 

SHAKING. 

Purpose. — The  purpose  of  shaking  the  evaporated  milk  is 
to  mechanically  break  down  the  curd  that  may  have  been  formed 
in  the  process  of  sterilization  and  to  give  the  contents  of  the  cans 
a  smooth  and  homogeneous  body. 

The  high  temperatures  to  which  the  evaporated  milk  is  sub- 
jected in  the  sterilizer  have. a  tendency  to  coagulate  the  casein. 
In  the  case  of  normal,  fresh  milk  the  casein  coagulates  at  a  tem- 
perature of  269  degrees  F.  In  the  evaporated  milk,  made  from 
perfectly  normal  and  sweet,  fresh  milk,  the  casein  curdles  at 
much  lower  temperatures,  and  the  higher  the  ratio  of  concentra- 


160 


EVAPORATED  MILK — SHAKING 


Tig.  68.    Evaporated  milk  shaker 

Courtesy  of  Arthur  Harris  &  Co. 


tion,  the  lower  the  temperature  required  to  precipitate  the 
casein.  It  seems  that  the  concentration  of  the  milk  intensifies 
the  properties  of  milk  to  coagulate  when  subjected  to  heat.  This 
factor  is  probably  in  part  at  least  due  to  the  increase  of  the  per 
cent  of  lactic  acid  in  the  evaporated  milk,  due  to  the  concentra- 
tion. If  the  fresh  milk  contains  .17  per  cent  lactic  acid,  a  con- 
centration of  two  and  one-fourth  parts  of  fresh  milk  to  one  part 
of  evaporated  milk  causes  the  evaporated  milk  to  contain  .17 
X  2.25  =  .38  per  cent  lactic  acid.  With  this  amount  of  acid 
acting  on  the  casein,  it  is  not  difficult  to  understand  why  a  coag- 
ulum  is  often  formed  in  the 
sterilizer.  While  the  formation 
of  this  coagulum  may  be  partly 
avoided,  under  certain  condi- 
tions it  appears  in  every  fac- 
tory and  there  are  more  batch- 
es, especially  in  summer,  that 
come  from  the  sterilizer  coag- 
ulated than  otherwise. 

In  this  condition  the  product  is  not  marketable.  Some  means 
must  be  provided,  therefore,  to  break  up  this  curd  and  reduce 
the  contents  of  the  cans  to  a  smooth,  homogeneous  and  creamy 
body.  For  this  purpose  a  mechanical  shaker  is  used. 

Method  of  Shaking. — The  shaker  consists  of  one  or  more 
heavy  iron  boxes,  or  iron  crates  made  of  black  iron  pipes.  These 
boxes  are  at- 
tached to  an 
eccentric.  The 
trays  filled 
with  evaporat- 
ed milk  cans 
are  firmly 
wedged  into 
these  b  o  x  e  s. 
When  the 
shaker  is  in 
operation,  the 

cans  are  shaken  back   and   forth   violently,   causing  the  curd   in 
the  cans  to  be    broken    up. 


Fig.  69.     Evaporated  milk  shaker 
Courtesy  of  The  Engineering  Co. 


EVAPORATED  MILK — SHAKING 


161 


Speed  of  the  Shaker. — If  the  shaker  is  to  perform  its  work 
properly,  it  must  have  long  enough  a  stroke  and  run  fast  enough 
to  cause  most  vigorous  agitation.  The  stroke  should  be  not  less 
than  about  two  and  one-half  inches  and  the  eccentric  should 
revolve  not  less  than  three  hundred  to  four  hundred  times  per 
minute.  In  order  to  accomplish  this  without  wrecking  the  ma- 
chine, the  shaker  must  be  fastened  securely  to  a  solid  foundation. 

From  one-fourth  to  two  minutes'  shaking  is  usually  suffi- 
cient to  completely  break  down  a  soft  curd.  When  shaking  for 
five  minutes  does  not  produce  a  smooth  milk,  the  product  is 
usually 'hopelessly  curdy  and  no  amount  of  additional  shaking 
will  remedy  the  defect. 

In  some  cases  it 
lias  been  possible,  how- 
ever, to  improve  the 
curdy  product  by  shak- 
ing again  after  a  day 
or  two.  Under  certain 
conditions,  age  seems 
to  have  a  slight  mel- 
lowing effect  on  the 
curd. 


Tig.  70.     Evaporated  milk  balanced  shaker 

Courtesy  of  Schaefer  Mfg.  Co. 


Formation  of  Curd  not  Desirable  nor  Necessary. — It  should 
be  understood  that  the  processor  should  aim  to  get  only  a  very 


Fig-.  71.     Atomatic  shaker 
Courtesy  of  Schaefer  Mfg.  Co. 


162  PLAIN  CONDENSED  BULK  MILK 

slight  and  soft  curd  in  his  product,  that  can  be  shaken  out  in 
the  shaker  in  one-fourth  to  one-half  minute.  When  the  curd 
produced  is  firm,  even  prolonged  shaking  will  not  prevent  the 
appearance  in  the  finished  product  of  specks  and  small  lumps 
of  curd.  Such  milk  is  rejected  on  the  market. 

The  formation  of  curd  during  the  sterilizing  process  is  not 
desirable  and  is  not  necessary  as  far  as  the  marketable  properties 
of  the  evaporated  milk  is  concerned.  It  is  unavoidable,  however, 
under  many  conditions  and  as  long  as  it  can  be  confined  to  a  soft 
curd  that  readily  shakes  out,  no  harm  is  done. 

INCUBATING. 

From  the  shaker,  the  cans  are  transferred  to  the  incubating 
room.  This  is  a  room  with  a  temperature  of  70  degrees  to  90 
degrees  F.  The  evaporated  milk  remains  there  ten  to  thirty  days. 
The  purpose  of  incubation  is  to  detect  defective  milk  and  de- 
fective cans  before  they  leave  the  factory.  If  the  contents  of 
any  of  the  cans  have  not  been  completely  sterilized,  or  if  any 
cans  have  the  minutest  leak,  the  evaporated  milk  therein  will 
spoil  within  the  time  of  incubation.  Such  milk  either  sours, 
curdles  or  becomes  solid,  or  it  undergoes  gaseous  fermentation, 
causing  the  appearance  of  "swell  heads/'  The  more  nearly  per- 
fect the  process  of  sterilization  and  the  better  the  construction 
and  seal  of  the  cans,  the  fewer  are  the  spoiled  cans.  This  incu- 
bation process  is  strictly  a  preventative  measure.  It  is  omitted 
in  many  factories  where  the  cans  are  labeled,  packed  and  ship- 
ped to  their  destination  at  once,  or  put  in  ordinary  storage  in 
the  factory. 

CHAPTER  XII. 

PLAIN  CONDENSED  BULK  MILK. 

Definition. — This  is  an  unsweetened  condensed  milk  made 
from  whole  milk,  or  partly,  or  wholly  skimmed  milk,  condensed 
in  vacuo  at  the  ratio  of  about  three  or  four  parts  of  fluid  milk  to 
one  part  of  condensed  milk.  It  is  usually  superheated  to  swell 


PLAIN  CONDENSED  BULK  MILK  163 

and  thicken  it,  and  it  has  the  consistency  of  rich  cream.  It  is 
sold  in  10-gallon  milk  cans  to  ice  cream  factories  and  in  milk 
bottles  to  the  direct  consumer.  Plain  condensed  bulk  milk  is 
not  sterile,  nor  is  it  preserved  by  sucrose.  Its  keeping"  quality 
is  similar  to  that  of  a  high  quality  of  pasteurized  milk. 

Quality  of  Fresh  Milk. — The  sweeter  and  purer  the  fresh 
milk  or  skim  milk,  the  better  will  be  the  quality  of  this  product. 
Old  milk,  or  skim  milk  in  which  the  acid  development  has  made 
considerable  headway,  tends  to  form  a  lumpy  plain  condensed 
bulk  milk.  However,  since  this  milk  is  not  subjected  to  steriliz- 
ing temperatures  and  is  used  up  quickly  after  manufacture,  the 
quality  of  the  fresh  milk  from  which  it  is  made,  is  not  of  such 
magnitude  as  in  the  case  of  evaporated  milk. 

Heating. — In  the  manufacture  of  plain  condensed  bulk  milk 
the  heating  is  accomplished  much  in  the  same  manner  as  in  the 
case  of  sweetened  condensed  milk  and  evaporated  milk.  The 
milk  is  usually  heated  by  turning  steam  direct  into  it;  though 
many  of  the  more  efficient  types  of  milk  and  cream  pasteurizers 
could  be  used  to  excellent  advantage  for  this  purpose. 

It  is  advisable,  however,  to  heat  this  milk  only  to  about  150 
to  160  degrees  F.  in  order  to  secure  a  nice  "liver"  (coagulum), 
when  it  is  superheated  in  the  pan.  If  the  milk  is  heated  to  the 
boiling  point  in  the  forewarm>ers,  it  does  not  respond  to  the 
superheating  in  the  pan  as  satisfactorily. 

Condensing. — The  condensing  of  plain  condensed  bulk  milk 
is  done  in  the  vacuum  in  a  similar  manner  as  described  under 
evaporated  milk,  except  that  the  evaporation  is  carried  farther. 
See  also  "Campbell  Process"  and  "Condensing  Milk  by  Continu- 
ous Process." 

Superheating. — AVhen  the  condensation  is  nearly  completed 
the  milk  in  the  pan  is  superheated.  This  is  accomplished  by 
shutting  off  the  steam  to  the  jacket  and  coils,  closing  the  valve 
that  regulates  the  water  supply  of  the  condenser,  stopping  the 
vacuum  pump  and  blowing  steam  direct  into  the  milk  in  the  pan, 
for  the  purpose  of  swelling  and  thickening  it.  During  this  proc- 


164 


PLAIN  CONDENSED  BULK  MILK 


ess  the  temperature  rises  to 
between  180  and  200  de- 
grees P.  When  the  milk 
lias  become  sufficiently 
thick  or,  in  the  language 
of  the  processor,  has  pro- 
duced the  "proper  liver" 
(coagulum)  the  steam  is 
shut  off,  water  is  again 
turned  into  the  condenser 
and  the  vacuum  pump  is 
started  up.  As  soon  as  the 
vacuum  has  risen  to  from 
twenty-five  to  twenty-six 
inches  and  the  temperature 
has  dropped  to  about  130 
degrees  F.  the  process  is 
complete,  the  vacuum  is 
released  and  the  condensed 
milk  is  drawn  off.  The 
superheating  usually  oc- 
cupies about  twenty-five 
to  thirty  minutes. 
The  completion  of  the  superheating,  or  the  point  when  the 
superheating  should  cease,  may  also  readily  be  detected  by  the 
examination  of  a  sample  of  the  product.  As  soon  as  the  con- 
densed milk  begins  to  show  a  flaky  condition  of  the  curd,  the 
purpose  of  superheating  has  been  accomplished.  The  amount  of 
superheating  necessary  and  that  the  milk  will  stand,  will  largely 
depend,  aside  from  the  sweetness  of  the  original  milk,  on  the 
extent  of  the  concentration.  The  higher  the  ratio  of  concentra- 
tion, the  less  superheating  is  required  to  secure  the  desired 
results. 

Striking.— -The  striking,  or  sampling  and  testing  for  gravity 
is  dorie-wfrK  k  Beaume  hydrometer,  the  same,  or  a  similar  one, 
as  is  used  for  evaporated  milk.  The  scale  should  extend  to  18 
degrees  Beaume.  The  batch  should  be  struck  before  and  after 
superheating. 

Factories  which  standardize  their  product  to  a  certain  estab- 


Fig-.  72.     Superheater 

Courtesy  of  C.  E.  Rogers 


PLAIN  CONDKNSED  BULK  MILK  165 

li.shed  density,  usually  condense  the  milk  to  a  point  slightly 
beyond  that  desired.  Then,  after  superheating,  they  determine 
the  amount  of  water  required  to  reduce  the  finished  product,  and 
then  add  the  required  amount  of  water  before  the  condensed  milk 
is  cooled.  It  is  advisable  to  use  destilled  water  for  this  purpose. 
Ratio  of  Concentration. — The  ratio  of  concentration  varies 
largely  with  the  fat  content  of  the  milk,  although  the  locality 
and  season  of  year  are  also  influencing  factors.  Whole  milk  is 
condensed  at  the  ratio  of  about  three  parts  of  milk  to  one  part 
of  condensed  milk,  while  the  ratio  of  concentration  for  skim 
milk  is  about  4  to  1.  The  proper  density  varies  somewhat  with 
locality  and  season  of  year.  Roughly  speaking,  whole  milk  has 
reached  the  proper  density  when  the  Beaume  reading  at  120  de- 
crees F.  is  about  10  decrees  P>.  and  skim  milk  has  reached  about 

o  o 

the  proper  density  when  the  Beaume  reading  at  120  degrees  F. 
is  about  14  degrees  15.  When  the  ratio  of  concentration  exceeds 
4  to  1,  there  is  danger  of  gritty  condensed  milk  due  to  the  pre- 
cipitation, in  this  concentrated  product,  of  crystals  of  milk  sugar 

Cooling. — The  plain  condensed  bulk  milk  is- usually  drawn 
into  40  quart  milk  cans,  placed  in  cooling  tanks  containing  re- 
volving cogwheels,  as  described  in  Chapter  VI,  under  ''Cooling 
Sweetened  Condensed  Milk."  and  is  cooled  to  as  near  the  freez- 
ing point  as  facilities  permit. 

Recently  this  crude  and  laborious  method  of  cooling  has 
been  superseded  in  many  of  the  larger  condenseries  by  more 
modern  ways.  While  the  plain  condensed  bulk  milk  becomes 
too  thick  and  sluggish  during  the  process  of  cooling  to  make 
possible  the  use  of  surface  coolers,  and  internal-tube  coolers,  it 
can  be  readily  cooled  in  vats  equipped  with  revolving  discs,  or 
in  horizontal  coil  vats  especially  constructed  for  this  purpose 
and  in  which  the  lower  part  of  the  vat  is  constricted  and  the  coil 
sets  very  low  in  this  constricted  part,  so  as  to  agitate  the  milk 
vigorously  and  at  the  same  time  prevent  the  incorporation  of  air, 
by  being  completely  submerged,  or  in  circular  vats  equipped 
with  a  vertically  suspended  coil.  The  vertical  coil  vat  has  the 
further  advantage  in  that  it  eliminates  from  the 'milk,  all  bear- 
ings and  glands  and  it  expels,  rather  than  incorporates,  air. 
from  the  condensed  milk. 

When  cooled  the  condensed  milk  is  rcadv  for  the  market. 


166  CONCENTRATED 

Jf  held  in  the  factory,  it  should  be  placed  in  a  cold  room  or 
should  be  otherwise  protected  against  temperatures  sufficiently 
high  to  cause  if  to  sour.  When  kept  at  -40  degrees  F.  or  below 
the  danger  from  souring  is  largely  eliminated.  If  transported 
long  distances  during  warm  weather,  it  should  be  shipped  in 
refrigerator  cars. 

CHAPTER  XIII. 
CONCENTRATED  MILK. 

Definition. — Concentrated  milk  is  cow's  milk,  either  whole 
milk,  or  partly  or  wholly  skimmed  milk,  condensed  at  the  ratio 
of  three  to  four  parts  of  fresh  milk  to  one  part  of  concentrated 
milk.  It  is  not  condensed  in  vacuo,  but  in  open  vats  by  passing 
currents  of  hot  air  through  the  milk.  It  is  sold  largely  in  pint 
and  quart  bottles  for  direct  consumption.  It  is  not  sterile  and 
therefore  keeps  for  a  limited  time  only.  Its  keeping  quality  is 
similar  to  that  of  a  high  grade  of  properly  pasteurized  milk.  The 
process  by  which  the  concentrated  milk  is  manufactured  is 
known  as  the  "Campbell  Process."  This  process  was  invented 
by  J.  H.  Campbell  of  New  York  City,  in  19CO  and  patented  in 
1901. 

Apparatus  Needed. — The  principal  parts  are:  the  evapo- 
rating vat  with  hot  water  jacket  and  coils,  and  air  blast  regis- 
ters or  nozzles  near  the  bottom  of  the  vat;  an  air  blower  which 
furnishes  the  air  blast;  an  air  heater  through  which  the  air 
blast  passes  and  from  which  the  heated  air  is  conducted  into  the 
milk;  a  water  pump  circulating  hot  water  through  the  jacket 
and  coils;  an  auxiliary  evaporating  tank  for  completing  the 
evaporation ;  and  a  spray  pump  which  throws  the  spray  of  milk 
drawn  from  the  bottom  of  the  main  evaporating  vat  into  the 
auxiliary  tank  and  for  transferring  the  partly  condensed  milk 
from  tank  1  to  tank  2. 

Operation  of  Campbell  Process. — The  milk  is  heated  to  about 
ICO  degrees  F.  and  allowed  to  flow  into  evaporating  tank  1. 
Water  at  temperatures  ranging  from  100  to  125  degrees  F.  is 
forced  through  the  coils  and  jacket.  Hot  air  is  then  passed  into 
the  milk.  The  temperature  of  the  air  is  regulated  so  as  to  keep 
the  temperature,  of  the  evaporating  milk  down  to  120  degrees  F. 


CONTINUOUS  PROCESS  EVAPORATORS  167 

on  the  start,  and  to  finish  the  evaporation  between  90  and  100 
degrees  F.  The  air  blast  is  so  introduced  as  to  keep  the  milk 
along  the  heating  surface  of  the  jacket  and  coils  in  circulation 
and.  therefore,  prevent  largely  the  baking  of  the  milk  on  the 
heating  surface.  After  the  milk  has  been  evaporated  to  a  certain 
degree  of  concentration,  say  2:1.  it  is  transferred  to  the  auxiliary 
evaporating  tank  where  the  condensation  is  completed.  This 
transfer  is  not  necessary,  but  is  resorted  to  solely  as  a  conve- 
nience, in  order  to  continue  treatment  of  the  reduced  bulk  of 
material  in  a  smaller  tank  and  leave  the  larger  tank  free  for 
treating  a  fresh  batch  of  milk,  and  further,  because  there  are 
no  obstructing  coils  in  the  auxiliary  tank,  interfering  with  the 
drawing  off  of  the  finished  and  thick  condensed  milk.  In  this  proc- 
ess, as  now  used,  the  milk  is  usually  first  separated  and  the 
skim  milk  only  is  condensed.  The  cream  is  subsequently  added 
to  the  condensed  skim  milk. 

Advantages  and  Disadvantages  of  Campbell  Process. — The 
initial  cost  of  installing  the  necessary  machinery  is  much  less 
than  where  vacuum  evaporation  is  practiced.  The  low  heat 
applied  makes  it  possible  for  the  finished  product  to  retain  the 
properties  of  raw  milk,  leaving  the  albumenoids  and  lime  salts 
in  their  original  and  easily  digestible  form  and  preserving  the 
antiscorbutic  vitamines  in  active  form. 

This  process  is  applicable  only  in  the  manufacture  of.  un- 
sweetened condensed  milk.  Unless  subsequently  sterilized,  the 
product  will  keep  for  a  short  time  only.  This  process  has  at  the 
present  time  only  very  limited  use.  It  can  hardly  be  considered 
as  an  important  branch  of  the  condensed  milk  industry. 

ClIAI'TKR    XIV. 

CONDENSING  MILK  BY  CONTINUOUS  PROCESS. 

The  processes  of  condensing  milk  described  in  preceding 
chapters,  are  exclusively  confined  to  the  intermittent  or  batch- 
principle  of  evaporation.  That  is  in  the  case  of  the  vacuum  pan, 
the  fresh  milk  runs  into  the  pan  until  the  capacity  of  the  pan  is 
reached  and  no  condensed  milk  leaves  the  pan  until  the  con- 
densation of  the  entire  batch  is  completed.  Then  the  pan  must 
be  emptied  before  more  milk  can  be  drawn  in.  In  a  similar  man- 
ner, in  the  Campbell  process,  evaporation  of  the  entire  batch 


168 


CONTINUOUS  PROCESS  EVAPORATORS 


must  be  completed  before  any  of  the  finished  product  leaves  the 
evaporating  vat  or  tank.  The  operation  in  either  case  is  inter- 
mittent and  not  continuous. 

Of  more  recent  years,  equipment  and  processes  have  been 
developed  that  make  possible  continuous  operation.  That  is,  the 
fresh  milk  enters  the  machine  and  the  condensed  milk  leaves  it 
simultaneously  and  continuously.  So  far  three  types  of  continu- 
ous machines  have  been  perfected  sufficiently  to  make  them  com- 
mercially practical  and  usable,  namely  the  Buflovak  Rapid  Cir- 
culation Evaporator,  invented  and  manufactured  by  the  Buffalo 
Foundry  and  Machine  Co.,  Buffalo,  N.  Y.,  the  Continuous  Con- 
centrator, invented  by  the  By-Products  Recovery  Co.,  Toledo, 
Ohio,  and  manufactured  by  the  Creamery  Package  Manufactur- 
ing Co.,  Chicago,  and  the  Ruff  Condensing  Evaporator,  manu- 
factured by  The  Cream  Production  Co..  Port  Huron,  Mich. 

BUFLOVAK  RAPID  CIRCULATION  EVAPORATOR. 

This  type  of 
Evaporator  has  been 
developed  from  the 
standard  return-flue 
tubular  boiler  and 
adopted  for  the  spe- 
cial purpose  of  han- 
dling foamy  and  del- 
icate liquors. 

Construction. — 
The  Buflovak  Rapid 
Circulation  Evapora- 
tor consists  of  a 
horizontal  cylindric- 
al vapor  body.  To 
this  is  bolted  an  in- 
c  1  i  n  e  d  cylindrical 
steam-chest. 

The  vapor  body 
is    equipped    with    a 
baffle  plate  which  ex- 
tends   across   its   cyl-      Pi?>  73.    The  Buflovak  rapid  circulation  evaporator 
illdncal        part        and  Courtesy  of  Buffalo   Foundry  &  Machine  Co. 


CONTINUOUS  PROCESS  EVAPORATORS  169 

leaves  openings  at  both  ends  of  the  vapor  body  for  the  vapors  to 
escape,  the  ends  or  heads  of  the  vapor  body  being  dished  out- 
ward. The  vapor  body  also  carries  the  milk  inlet,  vapor  outlet 
and  spy  glasses. 

The  steam  chest  which  is  attached  to  the  lower  part  of  the 
vapor  body,  is  divided  by  a  solid  partition  into  two  compart- 
ments. The  upper  and  larger  compartment  is  filled  with  tubes 
which  are  expanded  in  the  fine-sheets,  closing  both  ends.  The 
tubes  themselves  are  open  at  both  ends.  They  are  two  inches 
in  diameter  and  from  six  to  eight  feet  long.  The  lower  and  small 
compartment,  called  the  downtake.  is  entirely  open  at  both  ends. 
The  steam  chest  is  equipped  with  a  steam  inlet,  a  liquor  outlet 
and  a  condensation  outlet  or  drip.  The  steam  is  around  the 
tubes  and  the  milk  is  inside  the  tubes. 

Operation. — This  machine  is  operated  under  vacuum  of  from 
26  to  28  inches  mercury  column,  the  vapor  outlet  being  connected 
with  a  condenser  and  vacuum  pump. 

The  fluid  milk  enters  the  vapor  body  and  flows  down  into 
the  bottom  of  the  downtake  of  the  steam  chest,  from  where  it 
rises  in  the  tubes  and  finds  its  level.  The  level  of  the  milk  in 
the  tubes  is  kept  low,  the  coefficient  of  the  heat  transmission 
being  highest  when  the  milk  level  in  the  tubes  is  about  one- 
third  of  the  tube  length  above  the  lower  flue-plate,"  and  it  is 
regulated  by  automatic  float  controls  in  the  larger  machines. 
The  steam  that  is  turned  into  the  steam  chest,  causes  the 
milk  in  the  tubes  to  boil.  The  vapor  thus  arising  from  the 
milk,  together  with  a  portion  of  the  milk,  rises  and  passes 
through  the  upper  part  of  the  tubes  at  a  very  high  speed, 
and  is  thrown  with  great  force  against  the  ribs  of  the  baffle 
plate  which  extends  across  the  whole  cylindrical  length  of  the 
vapor  body. 

The  liquid  or  condensed  milk  returns  through  the  down- 
take  to  the  lower  part  of  the  steam  chest  where  it  escapes  from 
the  machine.  The  vapor  passes  at  both  ends  of  the  baffle  plate 
into  the  vapor  space  above  and  from  there  through  the  entrain- 
ment  separator  for  reclaiming  escaping  milk,  and  then  to  the 
condenser  attached  to  the  outlet  of  the  vapor  body. 

The  upper  part  of  the  tubes  becomes  covered  with  a  climb- 
ing film  of  milk.  .-This  together  with  the  high  speed  of  the 


170 


CONTINUOUS  PROCESS  EVAPORATORS 


milk  in  the  tubes  (100  feet  per  second  or  more)  increases  the 
capacity  of  the  heating  surface,  and  the  small  amount  of  milk 
in  circulation,  together  with  the  low  level  of  the  milk  in  the 
tubes,  reduces  the  possibility  of  foam  ing,  confining  the  foam  to 
and  breaking  it  up  in  the  upper  part  of  the  lubes  where  film 
evaporation  takes  place. 

The   escape   of   the   condensed   milk   is   continuous   and   the 


Fig-.  74.     Cross  section  of  Buflovak  rapid  circulation  evaporator 

Courtesy  of  Buffalo  Foundry  and  Machine  Co. 

degree  of  concentration  is  controlled  by  a  valve  regulating  the 
outlet.  The  condensed  milk  runs  by  gravity  from  the  steam 
chest  into  a  reservoir  located  under  the  evaporator.  In  this  case 
the  reservoir  must  be  under  the  same  vacuum  as  the  evaporator. 
In  some  cases  it  is  recommended  to  have  an  intermediate  storage 
tank  removing  the  condensed  milk  from  the  evaporator  by  a  spe- 
cially constructed  steam  pump. 


CONTINUOUS  PROCESS  EVAPORATORS  171 

THE  CONTINUOUS  CONCENTRATOR. 

The  inflow  of  the  fluid  milk  and  the  outflow  of  the  con- 
densed milk  are  continuous.  The  milk  is  condensed  under  atmos- 
pheric pressure  at  212  degrees  F.  A  rapidly  revolving  agitator 
throws  the  milk  in  a  thin  film  against  the  steam-heated  and  con- 
tinuously polished  periphery  of  a  jacketed  copper  drum.  By 
keeping  the  heating  surface  clean  and  bright,  and  the  milk 
rapidly  moving,  th,e  power  of  the  milk  to  absorb  and  utilize  heat 
is  greatly  augmented  and  the  rapidity  of  evaporation  increased. 

Description  of  Continuous  Concentrator. — The  continuous 
concentrator  consists  of  a  hollow  copper  drum.  The  copper  shell 
is  surrounded  by  a  steam  jacket  which  is  insulated.  The  space 


rig-.  75.    The  continuous  concentrator  with  preheater  and  cooler 

Courtesy  of  Creamery  Package  Mfg.  Co. 

between  inner  shell  and  jacket  is  about  one  inch. 

This  drum  carries  in  its  interior,  a  revolving  dasher  with 
four  or  more  blades,  according  to  the  size  of  the  machine,  and 
similar  to  an  ice  cream  freezer  or  a  flash  pasteurizer.  The  edge 
of  these  blades  comes  in  direct  contact  with  the  inner  surface 
of  the  shell  which  is  the  heating  surface,  so  that  when  revolving, 
each  blade  constantly  removes  from  the  heating  surface  any 
milk  that  adheres  to  it. 

The  blades  are  pressed  against  the  heating  surface  by  the 
centrifugal  force  that  is  generated  when  the  machine  is  in  mo- 
tion. The  arms  to  which  the  blades  are  attached  are  equipped 
with  stops  that  control,  their  pressure  against  the  heating  sur- 
face so  as  to  insure  continuous  and  uniform  pressure.  The  shaft 
which  carries  the  dasher  passes  through  the  front  and  rear  heads 


172 


CONTINUOUS  PROCKSS  EVAPORATORS 


of  the  concentrator  and  carries  a  pulley  back  of  the  rear  head, 
to  which  the  power  is  transmitted. 

The  rear  of  the  concentrator  terminates  in  the  exhaust 
chamber  of  the  condensed  milk  vapors,  which  escape  through  a 
galvanized  iron  flue  to  the  outside.  The  vapors  are  not  con- 
densed by  water,  but  escape  into  the  atmosphere.  The  rear  wall 
is  equipped  with  the  intake  of  the  fluid  milk.  In  order  to  permit 
the  milk  to  feed  the  concentrator  by  gravity,  without  necessitat- 
ing inconveniently  high  elevation  of  the  forewarmer,  the  intake 
is  located  at  the  bottom. 

In  the  front  head,  in  close  proximity  to  the  periphery  of  the 
concentrator  is  located  the  outlet  of  the  condensed  milk.  Its 
distance  from  the  inside  wall  of  the  concentrator  determines  the 
thickness  of  the  film  of  condensed  milk  that  is  allowed  to  form 
on  the  heating  surface,  and  the  amount  of  milk  that  is  retained 
in  the  concentrator.  According  to  the  amount  of  superheating 
intended,  this  film  may  vary  from  -J  to  -1-  inch  in  thickness  and 
the  amount  of  milk  retained  in  the  machine  may  vary  from  6 
to  12  quarts. 

The  front  head  is  equipped  with  a  cover  which  is  fastened 
to  the  rim  with  screw  bolts  and  which  carries  a  spy  glass  through 
which  the  operator  may  watch  the  process.  At  the  conclusion 
of  the  operation  this  cover  is  removed  and  the  dasher  and  blades 
are  taken  out,  so  that  both  the  shell  and  the  dasher  can  be 
readily  washed.  Over  the  top  of  the  concentrator  extends  the 
steam  line,  a  3  inch  pipe,  with  H  inch  laterals,  supplying  the 
steam  jacket,  and  insuring  uniform  distribution  of  heat.  The 
steam  line  is  also  equipped  with  regulator  and  steam  gauge.  At 
the  bottom  of  the  concentrator  is  located  the  exhaust  and  regu- 
lating crip  valve. 

The.  continuous  concentrator  is  constructed  of  diverse  sizes 
and  capacities,  the  most  common  of  these  sizes  are  the  following' : 


Diameter 

Length 

Capacity  per  Hour 
when  Concen- 
trating  at  the 
Ratio  of  3  :1 

Boiler  Capacity 
Required 
H.  P. 

3  feet 

4  feet 

7000  Ibs. 

100  If.  P. 

3  feet 

3  feet 

5000  Ibs. 

80  II.  P. 

3  feet 

2  feet 

2000  Ibs. 

40  H.  P. 

'  CONTINUOUS  PROCESS  EVAPORATORS  173 

Speed  of  Agitator.—  ^The  proper  speed  of  the  continuous 
concentrator  is  expressed  in  terms  of  rim  speed,  that  is  the 
distance  which  the  blades  travel  per  minute.  It  has  been  found 
that  the  rim  speed  which  is  sufficient  to  move  the  film  of  milk 
in  the  machine  properly,  is  about  2500  feet  per  minute.  In  order 
to  insure  a  rim  speed  of  2500  feet  per  minute,  the  blades  in  -a  3, 

2500 

foot  diameter  machine  must   revolve   —  —  —  —  —   265   times  per 

3x3.14 

minute.     In  a  six  foot  diameter  wheel,  the  same  rim  speed  would 


require    "*       .  •—  133  revolutions  per  minute  of  the  spider. 
6x3.14 

Again,  it  has  been  found  that  the  blades  should  be  not  more 
than  about  2\  feet  apart.  A  three  foot  diameter  concentrator, 
therefore,  requires  four  blades  while  concentrators  with  larger 
diameter  require  a  larger  number  of  blades  in  order  to  keep  the 
distance  between  blades  within  the  limit  of  two  and  one-half 
feet. 

Operation  of  Continuous  Concentrator.  —  The  operation  oi 
the  continuous  concentrator  is  simple  and  the  ratio  of  concen- 
tration of  the  product  can  be  regulated  as  desired. 

Heating  of  Milk.  —  Similar  as  in  .case  of  evaporation  in 
vacuo,  it  is  desirable,  if  not  necessary,  to  heat  the  milk  before 
it  enters  the  concentrator.  This  not  only  increases  the  capacity 
of  the  machine,  but  it  also  prepares  the  casein  in  the  milk  for 
the  superheating  to  which  the  milk  is  subjected  in  the  concen- 
trator. Any  method  of  forewarming  or  preheating  may  be  used 
for  this  purpose,  but  since  the  milk  flows  to  and  through  the 
concentrator,  in  a  continuous  stream,  it-is  preferable  to  also  use 
a  forewarmer  of  the  continuous  type.  The  milk  should  be  heated 
to  about  185  to  200  degrees  F.  and  the  forewarming'  should  be 
so  arranged  that  the  milk  is  exposed  to  this  temperature  for  5 
to  10  minutes  before  it  enters  the  concentrator. 

Condensing.  —  -The  concentrator  is  steamed,  the  parts  of.  the 
agitator  are  assembled  and  installed  in  their  proper  place,  the 
cover  is  securely  bolted  over  the  opening  in  the  front  head  and 
the  machine  is  ready  for  operation.  Before  starting  the  agitator 
a  small  amount  of  milk  is  permitted  to  flow  into  the  concentrator 


174  CONTINUOUS  PROCESS  EVAPORATORS 

so  as  to  prevent  the  blades  from  running  over  the  dry  heating  sur- 
face, cutting  the  copper.  Simultaneously  with  the  starting  of  the 
agitator  the  steam  is  turned  into  the  jacket  and  then  the  milk 
intake  valve  is  opened. 

The  steam  pressure  on  the  jacket  is  kept  uniform,  preferably 
at  40  to  50  Ibs.  of  steam.  This  machine  evaporates  the  milk  at 
atmospheric  pressure.  The  temperature  of  the  milk  in  the  con- 
centrator therefore,  is  practically  the  same  as  that  of  boiling 
water — 212  degrees  F. — at  the  sea  level  and  varies  only  with  the 
altitude  of  the  location.  The  ratio  of  concentration  is  regulated 
by  the  rate  of  the  mjilk  inflow.  As  the  milk  inflow  is  increased, 
the  ratio  of  concentration  is  reduced,  because  the  amount  of 
evaporation  being  constant,  a  smaller  proportion  of  the  water  is 
taken  out  of  the  milk. 

The  density  is  determined  by  the  use  of  the  Beaume  hydro- 
meter. If  the  density  is  greater  than  desired,  more  milk  is 
allowed  to  flow  into  the  machine.  If  the  density  is  lower  than 
desired  the  inflow  of  milk  is  reduced. 

Cooling  of  Condensed  Milk. — From  the  discharge  spout  the 
condensed  milk  is  run  over  a  continuous  cooler  from  which  it 
escapes  ready  for  packing  in  whatever  form  it  is  intended  for. 
The  disc  continuous  cooler  has  proven  very  suitable  for  this 
purpose. 

No  subsequent  superheating  of  the  concentrated  milk  is 
necessary.  This  product  can  be  made  of  any  consistency  desired, 
regardless  of  concentration,  according  to  the  thickness  of  the 
film  that  is  allowed  to  form  in  the  concentrator,  and  this  in  turn 
depends  on  the  distance  of  the  discharge  from  the  periphery  of 
the  machine. 

THE  RUFF  CONDENSING  EVAPORATOR. 

Principle  of  Machine  and  Process. — In  the  "Ruff  Condensing 
Evaporator,"  similar  as  in  the  "Continuous  Concentrator/'  the 
condensing  is  accomplished  by  the  film  principle,  but  in  the  Ruff 
machine  the  heating  surface  consists  of  one  or  more  steam-heated, 
revolving  drums,  and  atmospheric  air  is  blowrn  through  the  milk. 
This  machine  is  applicable  both,  for  continuous  evaporation 
and  for  condensing  in  batches. 


CONTINUOUS  PROCESS  EVAPORATORS 


175 


Construction. — The    Ruff   Condensing    Evaporator   consists 
of    the    follow- 
ing three  main 
parts : 

1.  A    vat   or 
tank     holding 
the  milk   to  be 
condensed,   and 
equipped     with 
cover.      The 
body      of      this 
tank  is  of  steel 
sheathing,     lin- 
ed on  the  inside 
with     tinned 
copper.    The 
cover  or  top  is 
fitted      with 
doors. 

2.  O  n  e   o  r 
more   steam- 
heated      hollow 

cylinders  which  revolve  in  the  tank  horizontally.  These  cylin- 
ders are  constructed  of  special  steel,  highly  polished.  They  are 
equipped  with  tinned  bronze  scrapers  which  remove  the  film  of 
milk  from  the  heating  surface.  The  cylinders  are  fitted  with 
a  device  for  the  automatic  removal  of  the  condensed  steam,  facil- 
itating the  continuous  heating  with  dry  steam  and  therby  in- 
hancing  the  rapidity  of  evaporation  and  augmenting  the  capacity 
of  the  machine. 

3.  An  arrangement   for  blowing  atmospheric  air  into  the 
lower  part  of  the  tank,  causing  it  to  rise  up  through  the  milk 
and  to  escape  from  the  tank. 

4.  Accessories. — The   entire    unit   further   comprises    such 
accessories  as   a   dial   thermometer,  high   pressure  blower  with 
pipe  connections  from  fan  "to  evaporator  and  automatic  return 
boiler  feed  pump,  complete. 

Operation. — The  milk  is  preheated  to  145  degrees  F.     The 
hot  milk  runs  into  the  tank  by  gravity,  or  is  pumped  in.     In  the 


Tig.  76.     Th«  Buff  condensing  •raporator 
Courtesy  of  The  Cream  Production  Co. 


176 


CONDENSED  BUTTERMILK 


case  of  continuous  evaporation  the  milk  is  kept  at  a  constant 
level,  the  lower  part  of  the  revolving  cylinders  dipping  into  it 
and  picking  up  a  film  which  is  automatically  scraped  off  with 
every  revolution  of  the  cylinders. 

At  the  same  time  air  is  blown  through  the  hot  milk,  further 
assisting  in  the  evaporation  and  also  removing  gases  and  other 
volatile  substances  from  tj^f  milk. 

During  operation  the-l^polving  cylinders  are  charged  with 
40  pounds  of  steam  and  the"  temperature  of  the  milk  is  held  at 
about  145  degrees  F. 

The  process  of  condensing  can  be  carried  to  almost  any  de- 
gree of  concentration  and  the  desired  degree  of  density  is  deter- 
mined in  a  similar  manner  as  in  the  case  of  evaporated  milk 
and  plain  condensed  bulk  milk. 

Capacity. — This  machine  is  constructed  in  several  sizes, 
with  capacities  ranging  from  900  pounds  to  8000  pounds  of 
raw  milk  per  hour,  based  on  a  ratio  of  concentration  of  two 
to  one,  as  shown  in  the  following  specifications : 


Additional  H    P 

Model  No. 
1920 

Number  of 
Steam 
Cylinders 

Approximate 
Floor  Space 

Gallons 
Tank 
Capacity 

Pounds    Capacity 
Condensing 
Raw  Milk 
2  to  1  per  Hour 

Required  for 
Blower     and 
Evaporator  Cyl- 
inders 

Required 
Boiler 
Capacity 
H.  P. 

"2 

2 

3'x5' 

175 

900 

4 

15 

•4 

2 

3'xlO' 

300 

1800 

7 

30 

6 

2 

4'xl4' 

500 

2700 

10 

40 

.  7 

4 

5'xl4' 

600 

5400 

20 

80 

8 

6 

7'xl4' 

1000 

8000 

30 

120 

Quality  of  Products  from  Continuous  Concentrators  and 
Evaporators.— -When  properly  operated  and  when  using  a  good 
quality  of  raw  material  these  continuous  concentrators  and  film 
evaporators  yield  a  product  of  excellent  flavor  and  good  quality, 
especially  suitable  for  the  manufacture  of  ice  cream,  but  also 
applicable  for  the  manufacture  of  sterilized  evaporated  milk, 
condensed  buttermilk  and  condensed  whey. 

CHAPTER  XV. 
CONDENSED   BUTTERMILK. 

*•<?*.'  The   vallre   of  buttermilk  as  a   part  of  the  feed  ration  for 
chickens,  laying  hens,  pigs  and  hogs  has  long  been  recognized 


CONDENSED  BUTTERMILK 


177 


and  its  use  for  feeding  purposes  is  rapidly  growing.  Buttermilk 
not  only  contains  protein  and  carbohydrates  of  high  quality  and 
great  digestibility,  but  it  has  biological  properties  that  stimulate 
growth  and  gain  in  weight,  and  it  exerts  a  physiological  action 
that  makes  for  a  healthy  condition  of  the  intestines,  because 
of  its  lactic  acid  content. 

Chicken  feeders  have  found  it  invaluable  in  their  efforts  to 
accomplish  maximum  growth  and  gain  in  weight  of  the  growing 
chicks,  and  because  of  the  superior  quality  of  the  meat  of  butter- 
milk-fed fowl.  And  extensive  experiments  with  laying  hens 
have  conclusively  demonstrated  that  buttermilk  makes  for  in- 
creased egg  production. 

For  similar  reasons  buttermilk,  when  properly  balanced  with 
other  feed,  is  a  most  valuable  hog  feed.  In  fact  it  is  the  founda- 
tion of  a  good  hog  and  is  becoming  a  more  and  more  indis- 
pensable part  of  the  ration  for  growing  pigs  and  fattening  hogs. 

Composition  of  Buttermilk.1 


Constituents 
in 
Buttermilk 

From    Ripened    Cream 

From  Sweet  Cream 

Van 

Slyke 

% 

Storch 
% 

Snyder 

% 

Vleth 

% 

Fleisch- 

ruann 
% 

Storch 
% 

Rich- 
mond 
% 

90.98 
.35 

3.51 

/  4.4? 
1     .01 
.73 

Water    

90.6 
.1 
2.8 

.8 
4.4 
.6 

.7 

90.93 
.31 

)  3.37 
4.58 

.81 

90.5 
.2 

3.3 
5.3 

.7 

90.39 
.50 

3.60 

4.06 

.75 
.80 

91.30 
.50 

3.50 

)  4.00 
.70 

89.74 
1.21 

3.28 

4.98 
.79 

Fat   

Casein    

Albumin    .... 
Milk  Sugar... 
Lactic  Acid  .  . 
Ash    

Specific   gravity   of   sweet-cream   buttermilk    1.0331. 

Specific  gravity  of  sour-cream   buttermilk   1.0314. 

Caloric  value   165. 

Since  the  great  bulk  of  butter  is  manufactured  during  the 
summer  season,  the  main  supply  of  buttermilk  is  confined  to  the 
summer  months.  In  summer  the  output  of  buttermilk  far  exceeds 
the  demand  for  this  product  and  much  of  it  goes  to  waste  for 
lack  of  a  suitable  market  for  it.  In  winter,  on  the  other  hand, 
the  output  of  buttermilk  is  small  and  insufficient  to  supply  the 
demand. 

1  Hunzlker,  The  Butter  Industry,  1920. 


178  CONDENSED  BUTTERMILK 

In  order  to  stop  this  waste  of  buttermilk  in  summer,  to  utilize 
it  economically  and  profitably  and  to  equalize  the  supply 
throughout  the  year,  some  of  the  large  creameries  of  the  coun- 
try have  found  it  practicable  and  profitable  to  condense  the  sur- 
plus buttermilk.  Information  from  chicken  feeders  and  hog 
feeders  shows  that,  when  re-diluted  to  the  consistency  of  the 
original  buttermilk,  this  condensed  buttermilk  gives  equally  as 
satisfactory  results  as  the  fresh  buttermilk. 

Prior  to  the  great  war  the  market  value  of  buttermjlk  and 
of  condensed  buttermilk  was  considered  too  limited  to  justify  the 
relatively  high  manufacturing  expense,  incident  to  the  concen- 
tration of  buttermilk  by  evaporating  from  it  a  large  portion  of 
its  water.  But  the  food  and  feed  shortage,  together  with  the 
high  prices  brought  about  by  the  war  and  since  the  war,  neces- 
sitated the  more  general  use  of  byproducts  and  raised  the  valua- 
tion of  buttermilk  to  figures  that  render  its  manufacture  into 
condensed  buttermilk  highly  profitable. 

Manufacture. — There  are  several  methods  whereby  butter- 
milk can  be  and  is  being  commercially  reduced  in  volume.  The 
most  common  of  these  are :  Removal  of  water  by  gravity,  re- 
moval of  water  by  centrifugal  separation,  removal  of  water  by 
evaporation,  either  in  vacuo  or  under  atmospheric  pressure. 

Removal  of  Whey  by  Gravity. — Much  of  the  so-called  con- 
densed buttermilk  that  reaches  the  market  is  not  the  result  of 
evaporation  of  a  portion  of  the  water  contained  in  the  butter- 
milk, but  is  produced  by  permitting  the  curd  to  settle  by  gravity 
and  then  drawing  off  and  rejecting  the  whey. 

In  this  case  the  fluid  buttermilk  is  pumped  into  a  wooden 
tank,  either  a  horizontal  vat  or  a  vertical  stave  tank.  The  tank 
usually  contains  several  outlets  with  gates,  located  at  different 
heights,  to  facilitate  the  removal  of  the  whey.  The  tank  may 
or  may  not  be  equipped  with  steam  pipes  for  heating.  The  but- 
termilk is  heated  to  boiling  point  in  these  tanks  either  by  blow- 
ing live  steam  into  it.  or  by  running  steam  through  the  pipes 
installed  in  the  tank.  This  heat  is  maintained  for  several  hours. 
This  causes  the  casein  to  contract  and  settle  to  the  bottom  in  the 
form  of  fine  particles  of  curd,  leaving  on  top  a  clear  whey.  This 
whey  is  drawn  off  through  the  gates  located  above  the  stratum 


CONDENSED  BUTTERMILK  •      179 

of  curd.  The  residue,  consisting  largely  of  casein,  water  and 
some  lactic  acid  and  milk  sugar,  represents  the  condensed  butter- 
milk. The  concentration,  or  more  correctly  speaking,  the  reduc- 
tion in  volume  thus  offered,  is  at  the  ratio  of  about  4  to  5  parts 
of  fluid  buttermilk  to  one  part  of  condensed  buttermilk.  It  is 
obvious  that  in  this  form  of  concentration  all  of  the  valuable  food 
elements  of  the  buttermilk  are  not  reclaimed.  Most  of  the  milk 
sugar  and  much  of  the  lactic  acid  escape  with  the  whey  and  are 
lost.  However,  the  equipment  required  for  this  process  is  very 
simple  and  inexpensive  and  the  process  requires  no  special 
knowledge  on  the  part  of  the  creamery  personnel. 

Concentration  by  Centrifugal  Separation. — For  many  years, 
efforts  have  been  made  to  remove  the  water  from  the  buttermilk 
by  centrifugal  separation.  Machines  are  now  on  the  market  and 
in  use,  in  which  the  curd  of  the  buttermilk  collects  on  the  walls 
of  a  revolving  basket  while  the  whey  is  centrifuged  out.  These 
machines  are  similar  in  principle  to  the  well-known  laundry 
centrifuge.  They  have  been  successfully  used  by  creameries 
that  are  engaged  in  the  manufacture  of  buttermilk  cheese.  Their 
operation,  however,  is  intermittent  only.  When  the  basket  fills 
up  with  the  curd,  the  machine  must  be  stopped  and  the  curd 
removed. 

For  the  purpose  of  handling  large  volumes  of  buttermilk 
daily,  these  centrifuges  are  obviously  not  well  adapted.  They 
are  too  limited  in  capacity,  in  speed  and  in  volume  of  per- 
formance. Efforts  to  devise  a  centrifuge  for  continuous  opera- 
tion, similar  to  the  cream  separator,  have  so  far  failed.  The  spe- 
cific gravity  of  the  curd  in  the  buttermilk  is  so  nearly  like  that 
of  the  whey,  that  the  centrifugal  separator  refuses  to  discharge 
a  liquid  rich  in  curd  and  one  of  practically  clear  whey.  Exper- 
iments by  the  author  have  demonstrated  that,  no  matter  how 
the  outlets  of  the  discharges  are  adjusted,  both  liquids  have  prac- 
tically the  same  composition. 

Evaporation  in  Vacuo. — This  method  for  condensing  butter- 
milk is  rapidly  gaining  in  favor  and  today  vast  volumes  of  but- 
termilk are  concentrated  in  this  manner.  The  equipment  used 
and  the  method  of  operation  are  principally  the  same  as  those 
used  in  the  manufacture  of  condensed  milk  and  evaporated 
milk.  The  buttermilk  is  condensed  in  the  vacuum  pan. 


180      •  CONDENSED  BUTTERMILK 

Equipment  Necessaiy  to  Condense  from  5000  to  6000  Pounds 
of  Buttermilk  per  Hour: 

2  wooden  buttermilk  storage  tanks,  capacity  10,000  pounds 
each,  for  ripening  the  buttermilk ; 

1   6-foot   vacuum   pan   with   condenser; 

1  vacuum  pump,   vacuum  cylinder   18  inches  diameter  and 
20  inches  long;  if  ste'am  driven,  steam  cylinder,  12  inches  diam- 
eter and    12  inches  stroke; 

2  hot  wells,  5  feet  diameter  and  5  feet  deep,  with  3  inch  out- 
let in  bottom,  and  equipped  with  brass  heater  arrangement. 

Boiler  capacity,  150  H.  P. 

Water  requirements,   125  gallons  per  minute. 

OPERATION. 

Ripening  of  Buttermilk. — The  buttermilk  should  be  sour, 
the  sourer  the  better,  because: 

1.  The  acidity  facilitates  the  process  of  manufacture.    The 
curd   in   sweet  or  only  slightly  sour  buttermilk   is   viscous  ajid 
sticky.    It  adheres  to  the  coils  and  sides  of  the  pan  and  its  action 
during  the  condensing  process  is  sluggish,  retarding  evaporation, 
reducing    the    capacity    of   the    pan    and    increasing   the   cost   of 
manufacture. 

If  the  buttermilk  is  sour,  these  handicaps  are  greatly  mini- 
mized. Upon  subsequent  heating  the  curd  in  the  sour  buttermilk 
contracts,  loses  much  of  its  viscosity  and  stickiness,  and  adheres 
less  readily  to  coils  and  sides  of  the  pan.  The  sour  buttermilk 
is  more  fluid,  boils  more  vigorously  and  therefore  condenses 
more  rapidly. 

2.  High  acid  content  is  necessary  in  order  to  give  the  con- 
densed   buttermilk    satisfactory    keeping   quality.      The    finished 
product  is  not  sterile,  nor  is  the  temperature  at  which  it  is  held 
in  storage  sufficiently  low  to  inhibit  bacterial  action  and  prevent 
decomposition.     The  acidity  is  essential  to  preserve  this  product. 

3.  High   acid   is   advantageous   for  feeding  purposes.     The 
acid  in  the  buttermilk  keeps  the  fowls,  pigs  and  hogs  in  healthy 
condition,   and   makes   them    thirsty.      They   drink   more   water, 
which  is  a  valuable  asset  for  best   results. 


CONDENSED  BUTTERMILK  181 

If  the  buttermilk  comes  from  sweet  cream  butter  or  from 
neutralized  cream  churnings,  it  is  usually  not  sufficiently  sour 
for  ready  handling  and  rapid  evaporation.  It  therefore  should 
be  allowed  to  ripen  before  it  is  used.  For  this  purpose  it  is  held 
in  wooden  storage  tanks  for  one  or  more  days,  where  it  auto- 
matically develops  acidity  due  to  the  lactic  acid  bacteria  with 
which  it  is  usually  teeming.  For  most  satisfactory  operation  the 
buttermilk  should  have  an  acidity  of  approximately  .6  per  cent. 
In  some  cases  it  may  be  necessary  to  inoculate  it  with  lactic 
acid  starter  in  order  to  insure  the  desired  acid  development. 

Heating  the  Buttermilk. — From  the  ripening  tanks  the  but- 
termilk is  drawn  or  pumped  into  the  hot  wells,  where  steam  is 
turned  direct  into  it  until  the  temperature  is  raised  to  the  boiling 
point.  This  method  of  heating  also  keeps  it  agitated  and  pre- 
vents the  copious  settling  of  the  curd. 

Condensing. — From  the  hot  wells  the  boiling-hot  buttermilk 
is  drawn  into  the  vacuum  pan.  The  buttermilk  is  preferably 
drawn  frrm  the  bottom  of  the  hot  wells,  so.as  to  continuously 
remove  a  portion  of  the  settling  curd.  The  buttermilk  will 
drop  some  of  its  curd  in  the  hot  wells.  The.  operation  of  the  vacu- 
um pan  for  buttermilk  is  the  same  as  for  milk.  For  general 
directions  the  reader  is  referred  to  Chapter  V  on  "Condensing." 

The  first  pans  used  for  condensing  buttermilk  were  tin 
coated  on  the  inside  and  had  tinned  copper  coils,  so  as  to  mini- 
mize the  action  of  the  acid  on  the  copper.  The  tin  coating  was 
of  very  short  duration,  however,  especially  that  on  the  coils,  so 
that  it  was  found  impractical  and  too  costly  to  use  tinned  vac- 
uum pans.  The  pans  now  in  use  are  not  tinned. 

In  the  condensing  of  a  thick  and  sluggish  liquid,  such  as 
buttermilk,  it  is  of  the  greatest  importance  that  the  coil  arrange- 
ment in  the  vacuum  pan  be  such  as  to  insure  maximum  circula- 
tion of  the  milk,  otherwise  the  buttermilk  is  incapable  to  absorb 
the  heat  fast  enough  and  to  expose  enough  surface  to  evapora- 
tion, to  make  possible  rapid  concentration,  the  buttermilk  fails 
to  freely  boil  up,  it  sluggishly  bubbles  in  the  bottom  of  the  pan, 
evaporation  is  slow,  the  capacity  of  the  pan  is  greatly  reduced, 
and  the  cost  of  manufacture  is  increased.  For  detailed  descrip- 
tion of  the  proper  coil  arrangement  see  Chapter  V  on  "'Descrip- 
tion of  Vacuum  Pan." 


182  CONDENSED  BUTTERMILK 

During  the  early  stages  of  the  condensing  process  the  but- 
termilk boils  and  behaves  in  the  pan  in  a,  similar  manner  as 
milk.  As  the  process  continues  and  the  buttermilk  increases 
in  density,  it  becomes  more  sluggish  and  does  not  circulate  as 
rapidly,  nor  boil  as  vigorously. 

Concentration. — The  buttermilk  should  be  condensed  until 
it  has  a  concentration  of  at  least  4:1.  Buttermilk  of  a  lower  con- 
centration fails  to  have  the  necessary  keeping  quality  to  with- 
stand the  trials  of  storage  for  several  months  at  ordinary  tem- 
perature. It  undergoes  decomposition,  usually  of  the  putrefac- 
tive type,  that  renders  it  unfit  for  feeding  purposes. 

Testing  for  Density. — No  accurate  mechanical  method  of 
determining  the  exact  density  of  the  condensed  buttermilk  has 
as  yet  been  worked  out.  When  a  concentration  of  about  4:1 
or  more  has  been  reached,  the  buttermilk  is  very  thick,  even 
while  hot.  It  is  too  thick  and  viscous  to  permit  of  testing  it 
with  the  Beaume  hydrometer.  The  density  could  be  determined 
however  by  weighing  a  definitely  measured  volume  or  by  the 
adaption  of  a  resistance  tester  such  as  the  Mojonnier  viscosi- 
meter.  Ordinarily,  however,  the  determination  of  the  proper 
degree  of  concentration  is  left  to  the  experienced  eye  and  judg- 
ment of  the  pan  operator.  If  he  condenses  batches  of  uniform 
size,  the  height  of  the  surface  of  the  condensed  buttermilk  in 
the  pan  furnishes  an  approximate  guide.  The  behavior  of  the 
boiling  condensed  buttermilk,  when  the  proper  degree  of  concen- 
tration has  been  reached,  is  also  noted.  And  samples  taken 
from  the  pan  and  examined  for  thickness,  standing-tip  properties 
and  transparency  or  opaqueness,  as  described  under  "Methods  of 
Striking11  for  sweetened  condensed  milk,  Chapter  VI,  enable  the 
operator  to  approach  a  fairly  uniform  density  of  the  finished 
product  from  batch  to  batch. 

When  condensed  at  the  ratio  of  4:1  the  buttermilk  at  the 
temperature  of  the  pan,  or  about  120  degrees  F.,  is  thick  enough 
so  that  when  a  sample  is  taken  into  a  cup  and  a  portion  of  it 
is  picked  up  with  a  spoon  or  stick  and  is  allowed  to  drop  back 
into  the  cup  from  a  height  of  about  six  inches,  it  does  not  readily 
diffuse,  but  "'piles  up"  on  the  surface  of  the  sample  in  the  cup. 

Condensing  Buttermilk  by  Film  Process. — The  condensing 
of  buttermilk  can  be  and  is  accomplished  also  by  film  evapora- 


CONDENSED  BUTTERMILK  183 

tion  as  represented  by  the  "Continuous  Concentrator"  and  the 
"Ruff  Condensing-  Evaporator."  These  methods  have  proven 
a  commercially  practical  proposition.  Experiments  have  demon- 
strated that  a  condensed  buttermilk  of  very  good  quality  and  of 
the  desired  degree  of  concentration  can  be  made  by  the  use  of 
these  continuous  machines.  In  fact  some  of  the  condensed  but- 
termilk on  the  market  is  their  product  and  it  is  probable  that 
the  future  will  see  many  of  these  machines  installed  and  in  opera- 
tion in  creameries  for  the  purpose  of  condensing  buttermilk. 
See  also  "Condensing  Milk  by  the  Continuous  Process,"  Chap- 
ter XIV. 

Packing. — The  condensed  buttermilk  is  filled  into  barrels, 
holding  about  600  pounds  of  the  finished  product.  Second  hand 
glucose  barrels  or  copra  barrels  are  generally  used  for  this  pur- 
pose. Buttermilk  intended  for  bakeries,  confectioners  and 
other  channels  of  human  consumption,  should  be  filled  into  new 
barrels.  The  barrels  should  be  thoroughly  rinsed  and  steamed  out 
before  use  and  it  is  advisable  to  treat  them  on  the  inside  with 
sodium  silicate. 

The  barrels  are  filled  with  the  condensed  buttermilk  while 
hot  and  direct  from  the  pan  or  other  condenser.  If  allowed  to 
cool,  the  condensed  buttermilk  would  be  too  thick  to  "run." 

Storage. — The  barrels  filled  with  the  condensed  buttermilk 
are  stored  at  ordinary  ware  house  temperature.  If  made  from 
properly  soured  buttermilk,  condensed  at  the  ratio  of  not  less 
than  4:1,  and  if  the  barrels  are  filled  completely  full  and  sealed 
tightly,  the  product  will  keep  in  good  condition,  without  mold- 
ing and  without  appreciable  deterioration  for  many  months 
without  artificial  refrigeration. 

In  remnant  barrels  or  in  barrels  which  are  subsequently 
opened  and  from  which  a  portion  of  the  contents  has  been 
removed,  the  buttermilk  molds  rapidly  on  the  surface  and  spoils, 
because  of  exposure  to  air.  This  can  be  largely  prevented  by 
"slapping"  a  piece  of  heavy  paper  (wrapping  paper),  large 
enough  to  cover  the  entire  exposed  surface,  on  the  top  of  the 
remaining  contents.  The  condensed  buttermilk  being  of  a  pasty 
consistency  forms  a  tight  seal  with  the  paper,  shutting  out  the 
air,  and  retarding  molding  and  decomposition. 

The   above   statements   concerning   the   keeping   quality   of 


184  ,  CONDENSED  BUTTERMILK 

condensed  buttermilk  refer  only  to  the  product  resulting  from 
evaporation  of  a  portion  of  the  water,  such  as  condensing  in  the 
vacuum  pan,  or  by  the  continuous  concentrators  and  evapora- 
tors. Where  the  reduction  in  volume  is  accomplished  by  re- 
moving a  portion  of  the  whey,  either  by  gravity  or  by  centrifugal 
separation,  the  finished  product  lacks  in  keeping  quality,  it  will 
spoil  in  a  few  weeks  after  manufacture,  if  held  at  ordinary  tem- 
peratures. The  reason  for  this  lies  in  the  fact  that  with  the 
removal  of  the  whey,  the  finished  product  is  also  deprived  of 
much  of  the  lactic  acid.  ~ There  is  not  high  enough  a  percentage  of 
acid  left  in  it  to  preserve  it. 

Composition  of  Commercial  Condensed  Buttermilk. 

Total    Solids 36  per  cent  to  40  per  cent 

Water   60  "           "64 

Fat     1  "           "      2 

Protein    12  "15 

Milk  Sugar    16  "20 

Acid    2  "      3 

Ash 2.5      "  "      3.5      " 

Caloric  Value 600  to          700 

Markets. — The  great  bulk  of  condensed  buttermilk  manu- 
factured in  the  United  States  is  sold  to  chicken  feeders  and  for 
hog  feeding.  The  price  obviously  fluctuates  with  season,  local- 
ity and  supply  and  demand.  During  the  first  six  months  of  1920 
it  averaged  about  4.5  cents  per  pound. 

Considerable  quantities  of  condensed  buttermilk  are  also 
absorbed  by  bakeries  and  manufacturers  of  diverse  prepared 
food  products.  The  price  received  during  the  first  six  months 
of  1920,  for  condensed  buttermilk  sold  to  bakeries,  etc.,  aver- 
aged about  8.5  cents  per  pound. 

Annual  Output  of  Condensed  Buttermilk  in  United  States. 
— As  previously  stated  the  manufacture  of  condensed  buttermilk 
is  rapidly  growing.  In  1918  the  total  output  amounted  to 
6,534,023  pounds;  in  1919  it  was  22,535,580  pounds. 

CONDENSED  WHEY,  MYSEOST,  OR  PRIMOST. 

The  condensing  of  whey  is  a  practice  which  originated  in 
Scandinavia.  The  original  process  consisted  of  straining  the 


CONDENSED  BUTTERMILK  185 

whey  into  a  kettle  or  large  open  pan  over  a  fire.  ^Thc  albumi- 
nous material  that  precipitates  and  rises  to  the  surface  is  skim- 
med off."1  The  whey  is  evaporated  as  rapidly  as  possible  with 
constant  and  thorough  stirring.  When  it  has  reached  about  one- 
fourth  of  its  original  volume  the  albumin  previously  skimmed 
off  is  returned  and  stirred  thoroughly  to  break  up  all  possible 
lumps.  When  the  whey  has  attained  the  consistency  of  thick- 
ened milk  it  is  poured  quickly  into  a  wooden  trough  and  stirred 
with  a  paddle  until  cool,  to  prevent  the  formation  of  large  sugar 
crystals.  Tt  can  then  be  molded  into  the  desired  form  for 
market. 

A  more  rapid  method  of  making  primost  is  to  evaporate  the 
whey  in  the  vacuum  pan.  When  the  syrup  has  reached  the 
desired  density  it  is  drawn  off,  allowed  to  cool  and  pressed  into 
bricks.  The  product  has  a  yellowish-brown  color,  gritty  texture 
and  sweetish  taste.  The  evaporation  of  whey  in  vacuo  is  as  yet 
a  rare  practice  and  the  demand  for  the  finished  product  is  very 
limited. 

Experiments  with  the  "Continuous  Concentrator"  have 
demonstrated  that  condensed  whey  of  good  quality  can  readily 
be  prepared  with  this  machine.  The  concentration  can  be  car- 
ried as  far  as  15  to  1  ;  whey  so  condensed  escapes  from  the  con- 
centrator still  in  liquid  form,  but  changes  to  a  solid  upon  cool- 
ing, the  milk  sugar  in  this  supersaturated  solution  crystallizing 
completely.  If  made  of  sour  whey,  the  product  thus  obtained 
has  a  splendid  clean  and  sharp  acid  flavor.  This  product  prom- 
ises to  have  excellent  dietetic  properties,  and  also  to  lend  itself 
admirably  for  cooking  purposes. 

1  United   States  Department   of  Agriculture,   Bureau  of  Animal   Industry, 
Bulletin  No.   105. 


PART  IV. 
FROM  FACTORY  TO  CONSUMER 

CHAPTER    XVI. 

Stamping. — Every  well  regulated  condensing  factory,  selling 
condensed  milk  in  hermetically  sealed  tin  cans,  employs  some 
system  of  marking  the  cans.  This  is  important  for  future 
reference. 

When  defective  condensed  milk  is  returned  to  the  factory, 
the  marks  on  the  cans  tell  the  manufacturer  the  date  of  manu- 
facture, and  his  own  record  on  file  in  the  factory  shows  the  con- 
ditions under  which  the  defective  milk  was  made.  In  this  way 
defects  can  usually  be  traced  to  their  causes  and  the  recurrence 
of  similar  trouble  can  be  avoided. 

In  some  factories  the  batches  of  condensed  milk  are  num- 
bered from  one.  up,  and  the  cans  are  stamped  with  the  respective 
batch  number.  This  method  is  simple  but  may  prove  undesirable, 
since  it  informs  the  competitors  also  of  the  date  of  manufacture 
of  competing  brands.  In  most  factories  a  code  of  letters  and 
figures  is  used,  designating  the  factory,  the  date,  and  the  number 
of  the  batch  of  each  day. 

The  cans  are 
usually  stamp- 
ed on  the  bot- 
tom, that  is,  on 
the  end  which 
carries  the  cap. 
The  stamping 
is  done  by  the 
sealer.  Small 
interchangeable 
rubber  letters 
and  figures  are 
u  s  e  d.  The 

stamping     i  n  k 

Mojonnier  evaporated  milk  can  polisher          chrfiilH     ' 
Courtesy    Mojonnier    Bros.    Co.  SHOUld 


Tig.  78. 


LABELING  CANS  187 

a  drier  and  be  waterproof.  In  small  factories  the  stamping  is  done 
by  hand.  It  can  be  done  very  rapidly.  In  large  factories  an  auto- 
matic stamping  outfit  is  attached  to  the  filling,  sealing  or  labeling 
machine  and  the  cans  are  stamped  automatically  while  they  are 
being  filled,  sealed  or  labeled. 

Inspecting. — The  sealed  and  stamped  cans  are  placed,  with 
caps  down,  in  wooden  trays  holding  twenty-four  medium-sized 
cans.  All  trays  of  one  batch  are  stacked  together.  A  card  in- 
dicating number  and  date  of  batch  and  number  of  cans  in  the 
batch  is  attached  to  the  stack  and  a  copy  of  the  same  is  filed  in 
the  office.  The  cans  are  placed  with  their  caps  down  in  order  to 
detect  "leakers"  (cans  with  defective  seals).  Before  labeling, 
the  trays  should  be  taken  down,  the  cans  turned  over  and  exam- 
ined for  leaky  seals.  Unless  the  factory  is  behind  in  filling-  orders 
the  cans  will  have  been  in  stock  at  least  twenty-four  hours  or 
usually  longer.  In  the  case  of  sweetened  condensed  milk,  if  any 
seals  are  defective,  a  little  condensed  milk  will  have  oozed  out 
by  that  time.  Inexperienced  sealers  are  prone  to  cause  a  high 
percentage  of  leaky  cans.  A  careful  sealer  may  reduce  the  num- 
ber of  leakers  to  .1  per  cent. 

In  the  case  of  evaporated  milk  (unsweetened,  sterilized)  all 
cans  coming  from  the  incubating  room  should  be  individually 
shaken  by  hand.  All  cans  showing  no  signs  of  bulging,  and  the 
contents  of  which  shake  with  the  characteristic  sound  and  be- 
havior of  a  liquid,  pass  inspection.  If  the  ends  of  the  cans  are 
bulging  or  the  contents  do  not  respond  to  the  shaking  with  the 
characteristic  sound  of  normal  milk,  they  are  rejected,  as  the 
evaporated  milk  in  them  has  either  undergone  gaseous  or  cur- 
dling fermentation,  and  is  spoiled. 

LABELING. 

Labeling  Machines. — In  the  early  days  of  the  milk  condens- 
ing industry,  the  labeling  of  the  cans  was  done  by  hand,  involv- 
ing much  time  and  considerable  expense.  Today,  especially  con- 
structed labeling  machines  are  almost  exclusively  used  for  this 
purpose.  The  efficiency  and  quality  of  work  of  these  machines 
are  such,  that  they  have  become  a  permanent  fixture  in  practi- 
cally every  condensery  selling  canned  goods.  The  labeling  ma- 


188  LABEUNC;  CANS 

chines  are  adjustable  to  various  sizes  of  cans  and  can  he  oper- 
ated by  hand,  motor,  or  belt  power. 

Principle  of  Labeling  Machines. — The  cans  are  placed  into 
a  chute  from  which  they  roll  into  the  machine  by  gravity.  They 
are  caught  by  two  endless  belts  which  draw  them  through  the 
machine  They  first  pass  over  revolving  metal  discs  that  touch 
each  can  with  a  trace  of  "pick-up"  cement.  From  here  the  can 
rolls  over  the  label  table  which  is  loaded  with  a  stack  of  labels, 
face-down.  The  touch  of  "pick-up"  cement  on  the  cans  causes 
each  can  to  pick  up  one  label,  which  is  automatically  wrapped 


Fig*.  79.     Burt  labeling-  machine 
Courtesy  of  Burt  Machine  Co. 

around  the  can  as  it  rolls  on.  An  endless  belt  passing  through 
a  paste  box  applies  a  small  strip  of  paste  to  the  lap  of  the  label 
and  a  curling  rod  stretches  the  label  taut  and  gives  its  lap  an 
inward  curl,  making  it  to  conform  to  the  shape  of  the  can  and 
ensuring  a  perfect  seal. 

The  label  table  is  equipped  with  an  automatic  feeding  ar- 
rangement which  pushes  the  stack  of  labels  up  as  fast  as  the 
labels  are  being  used. 

Wrinkles  and  Rust  Spots  on  Labels. — In  the  latest  models 
of  labeling  machines  no  paste  touches  the  cans  proper.  The 
"pick-up"  cement  used  on  the  cans,  is  moisture-proof  and  is 
applied  hot.  This  is  a  great  advantage  from  the  standpoint  of 
ensuring  freedom  from  rust  spots  on  labels.  The  cement,  being 
applied  hot.  dries  instantly  and  having  no  corrosive  action  on  the 


PACKING  IN  CASKS  189 

can,  is  a  reliable  safeguard  against  wrinkles  and  rust  spots,  which 
are  so  prone  to  appear  where  paste  is  used  exclusively,  and  which 
mar  the  attractiveness  and  neatness  of  the  package.  The  labeled 
cans  which  now  leave  the  machine  over  a  chute  slanting  from  it, 
can  be  cased  immediately  without  risk.  The  use-  of  tables  and 
fans  to  dry  the  labels,  often  found  necessary  in  the  case  of 
mechanically  applied  paste,  is  made  superfluous,  and  time,  labor 
and  space  are  saved. 

Capacity  of  Labeling  Machines. — In  the  latest  improved 
types  of  labeling  machines  the  capacity  has  been  greatly  in- 
creased over  that  of  the  older  models.  One  properly  operated 
hand-driven  machine  will  now  label  on  an  average  from  40,000 
to  50,000  cans  and  a  power-driven  machine  will  average  from 
60;OQO^to  70,000  cans  per  ten-hour  day. 

PACKING. 

The  labeled  cans  are  packed  in  cases  holding  from  six  to 
ninety-six  cans,  according  to  the  size  of  the  cans.  (One  case 
holds  six  1-gallon  cans;  forty-eight  14-,  15-,  16-.  and  20-ounce 
cans;  or  seventy-two  to  ninety-six  S-oimce  cans.) 

The  sides,  bottom  arid  top  of  the  cases  should  be  of  material 
about  three-eighths  of  an  inch  to  one-half  inch  thick,  the  ends 
three-fourths  of  an  inch  to  seven-eighths  of  an  inch  thick.  The 
cases  are  usually  bought  in  the  "knock-down"  shape  and  are 
made  up  in  the  factory.  Sixpenny  cement-coated  wire  nails  are 
most  suitable  for  this  purpose.  The  cases  are  most  economically 
nailed  by  the  use  of  nailing  machines,  which  nail  one  entire  side 
or  one  side  and  one  end  simultaneously.  The  cans  are  usually 
placed  into  the  cases  direct  from  the  labeling  machine.  In  some 
factories,  packing  machines,  which  pack  twenty-four  medium- 
size  cans  in  one  operation,  are  used.  Formerly  condensed  milk 
cans  were  packed  exclusively  in  wooden  cases.  Within  the  last 
few  years  the  use  of  paste-board  and  ribre  boxes  has  been  adopted 
in  many  condenseries.  These  boxes  are  proving  very  serviceable 
for  domestic  trade,  and  prior  to  the  price  advance  on  paper  ma- 
terial caused  by  the  world  war,  they  made  possible  a  considerable 
saving  in  the  cost  of  the  package. 

Mechanical  can  casers,  operating  with  the  labeling  machine, 
are  now  available  and  are  used  to  advantage  in  many  condens- 


190  PACKING  IN  CASES 

cries.  The  can  caser  receives  the  labeled  cans  from  the  labeling 
machine,  stacks  them  into  layers,  places  the  layers  of  cans  into 
the  case  and  automatically  pushes  off  the  filled  case,  while  a 
new  layer  of  cans  is  pushed  forward.  It  is  obvious  that  the 
mechanical  can  caser  makes  the  work  of  packing  the  cans  easier 
and  accelerates  its  speed. 

Marking  the  Cases. — One  end  of  each  case  is  stenciled  with 
the  number  of  the  batch ;  over  the  other  end  is  pasted  a  case 
label,  representing,  enlarged,  the  brand  of  the  label  on  the  cans 
within.  In  the  place  of  the  case  label,  the  respective  brand  may 
be  printed  on  or  burnt  into  the  wood.  The  burnt  stenciling  is 


Fig*.   80.     Burt  caser 

Courtesy  of  Burt  Machine  Co. 

usually  done  by  the  manufacturer  of  the  shocks.  One  side  of 
each  case  is  usually  marked  "Condensed  Milk"  or  "Evaporated 
Milk,"  as  the  case  may  be;  the  other  "Keep  in  cool,  dry  place." 
If  sweetened  condensed  milk  is  exposed  to  excessive  heat  for  a 
considerable  length  of  time,  as  is  often  the  case  in  storehouses 
or  in  the  hold  of  steamers,  where  the  cases  may  be  stowed  against 
the  boiler  room,  it  becomes  brown,  thickens  rapidly  and  develops 
a  stale  flavor.  Evaporated  milk  also  darkens  when  exposed  to 
heat  and  depreciates  in  flavor.  It  should,  therefore,  be  kept  in 
a  cool  place.  The  humidity  of  the  storage  room  has  no  effect  on 
the  condensed  milk  proper,  the  cans  being  hermetically  sealed. 


STORAGE  191 

Prolonged  exposure  to  dampness,  however,  will  dampen  and 
wrinkle  the  labels,  rust  the  cans  and  invite  the  appearance  of 
rust  and  mold  spots. 

Packing  Condensed  Milk  for  Export. — In  the  case  of  con- 
densed milk  bought  by  the  United  States  Government,  the  cans 
are  dipped  in  a  solution  of  shellac  before  they  are  labeled,  or  the 
tin  plate  or  empty  cans  are  .bought  by  the  manufacturer  already 
lacquered.  Cans  for  export  trade  and  in  many  instances  for  the 
home  market,  are  wrapped  into  heavy,  soft  paper,  bearing  on  the 
outside  a  copy  of  the  respective  brand.  This  wrapping  paper 
takes  up  the  space  beetween  the  cans  and  prevents  the  cans 
from  being  damaged  on  their  long  journey  and  by  rough  usage. 
This  wrapping  is  usually  done  by  hand.  Some  makes  of  label- 
ing machines,  however,  have  an  attachment  for  wrapping  the 
cans  so  that  wrhen  the  cans  leave  the  machine  they  are  wrapped 
as  well  as  labeled.  The  cases  are  reinforced  with  a  band  of  strap 
iron  around  each  end.  Where  the  cases  have  to  be  loaded  and 
unloaded  numerous  times,  as  is  the  case  with  export  shipments, 
they  are  in  danger  of  being  torn  to  pieces,  unless  such  special 
precautions  are  taken. 

CHAPTKR  XVII. 
STORAGE. 

Purpose  of  Storing. — The  purpose  of  storing  condensed  milk 
is  largely  the  same  as  that  of  storing  butter  and  other  produce, 
namely,  to  keep  the  product  from  the  time  of  large  supply  and 
low  prices,  to  the  time  of  small  supply  and  high  prices.  In  sum- 
mer time,  the  market  is  usually  flooded  with  condensed  milk 
throughout  the  country,  the  demand  for  it  is  at  ebb  tide  and  the 
prices  are  low.  In  winter,  there  is  usually  a  great  shortage  of 
condensed  milk,  the  demand  far  exceeds  the  supply  and  prices 
soar  high.  The  storing  of  summer  milk  may  be  necessary,  also, 
in  order  to  enable  the  manufacturer  to  fill  his  contracts  and  sup- 
ply his  trade  in  winter.  This  is  especially  true  where  the  fac- 
tories of  a  concern  are  located  in  newr  territories  where  the  pa- 
trons produce  an  excessively  small  amount  of  winter  milk. 

Plain  condensed  milk  and  concentrated  milk  which  are  not 
sterile  and  contain  no  cane  sugar  to  preserve  them,  keep  but  a 


192  STORAGE 

few  days  at  ordinary  temperatures  and  should,  therefore,  be  sold 
and  used  as  soon  as  possible  after  manufacture.  Tf  their  storage 
is  unavoidable,  they  should  be  held  as  near  the  freezing  point 
as  possible.  For  prolonged  storage  it  might  be  advantageous  to 
freeze  them.  However,  reliable  data  on  this  phase  of  the  indus- 
try are  lacking. 

Evaporated  milk,  sold  in  hermetically  sealed  cans,  is  sup- 
posed to  be  entirely  sterile,  and.  if  made  properly,  will  keep  in- 
definitely. There  is  a  constant  tendency,  however,  for  the  fat 
to  separate  out.  which  naturally  is  augmented  by  prolonged 
storage.  Again,  the  lactic  acid  in  the  evaporated  milk  gradually 
acts  on  the  can.  causing  the  tinplate  to  become  dull  and  the 
contents  to  acquire  a  disagreeable  metallic  flavor,  ^'hen  stored 
for  an  excessively  long  time  this  chemical  action  may  be  suffi- 
cient to  cause  the  evolution  of  considerable  quantities  of  hydro- 
gen gas.  swelling  the  cans. 

Sweetened  condensed  milk  which  is  preserved  by  about  40 
per  cent  of  sucrose,  will  keep  apparently  unchanged  for  a  con- 
siderable length  of  time.  It  is  best,  however,  when  fresh.  Bac- 
teriological examinations  have  shown  that,  while  moderate  age 
does  not  change  the  outward  appearance  of  this  condensed  milk, 
the  bacteria  in  it  gradually  increase  and  the  milk  gradually  de- 
velops a  stale  flavor.  White  and  yellow  "buttons."  lumps,  or 
nodules  of  a  cheesy  texture  and  flavor,  due  to  fungus  growth, 
are  also  prone  to  appear  in  the  condensed  milk.  Age,  also,  causes 
it  to  become  darker  in  color.  These  defects  are  especially  ap- 
parent in  old  milk  which  has  not  been  kept  at  a  low  temperature. 
Again,  sweetened  condensed  milk  made  in  May  and  June  has  a 
strong  tendency  to  thicken  with  age  and  to  become  entirely  solid. 

In  some  cases  a  part  of  the  sweetened  condensed  milk  marie 
during  the  summer  months  is  stored  in  large  cylindrical  wooden 
or  iron  tanks  sunk  into  the  ground,  or  installed  in  the  basement 
of  the  factory,  where  the  condensed  milk  remains  at  an  even  tem^ 
perature.  As  the  demand  for  the  product  increases  and  the 
supply  of  fresh  milk  decreases,  condensed  milk  is  drawn  from 
these  tanks  to  fill  the  increasing  orders. 

Effect  of  Storage  Temperature. — Most,  if  not  all  the  changes 
which  condensed  milk  is  prone  to  undergo  in  storage  are  retarded, 
if  not  entirely  prevented,  when  stored  at  the  proper  temperature. 


STORAGE 

Temperatures  of  60  degrees  F.  or  above  are  too  high  for  satis- 
factory storage  for  a  prolonged  period  of  time  and  the  higher 
the  temperature  the  greater  the  resulting  defect. 

Temperatures  below  the  freezing  point  of  water  are  also 
undesirable.  The  evaporated  milk  freezes  and  while  so  doing  it 
expands  sufficiently  to  swell  the  cans.  Although  this  swelling 
disappears  when  the  contents  of  the  cans  dissolve  again,  yet 
the  swelling  action  tends  to  weaken  the  cans  and  may  give  rise 
to  subsequent  leakers.  Again,  the  melted  evaporated  milk  is 
prone  to  be  grainy  as  the  result  of  freezing.  This  is  due  to  the 
fact  that  when  freezing,  the  watery  portion  separates  from  the 
curd  and  the  latter  contracts.  When  the  milk  thaws  up  the  curd 
remains  contracted  and  fails  to  form  a  smooth  emulsion  with 
the  remainder  of  the  milk. 

The  sweetened  condensed  milk  does  not  freeze,  because  it 
contains  so  concentrated  a  sugar  solution  that  its  freezing  point 
is  usually  far  below  the  refrigerating  temperature.  If  it  is  packed 
in  solder-sealed  cans  there  is  usually  no  bad  effect  from  cold 
storage.  However,  when  packed  in  cans  sealed  with  the  friction 
cap  or  the  burr  cap,  difficulties  may  arise.  These  seals  are  not 
air-tight.  Excessively  low  storage  temperatures  cause  the  con- 
tents to  shrink  appreciably.  Suction  is  formed  and  air  is  drawn 
in  through  the  seal.  When  these  cans  again  warm  up,  the  vis- 
cous milk  in  the  cans  seals  the  microscopic  openings,  the  air  and 
the  liquid  expand  but  the  air  finds  no  exit.  This  causes  the  cans 
to  swell.  While  the  quality  of  the  milk  in  these  cans  is  not  im- 
paired in  the  least,  the  swelled  cans  suggest  gaseous  fermenta- 
tion, which  means  spoiled  milk  and  which  is  invariably  rejected 
on  the  market. 

The  temperatures  at  which  condensed  milk  can  be  stored 
with  least  objectionable  results,  range  between  32  and  50  de- 
grees F. 

Advisability  of  Storing. — A  heavy  stock  of  condensed  milk 
is  a  severe  drain  on  the  working  capital  of  the  condensery,  in- 
volving the  cost  of  the  fresh  milk,  cane  sugar,  tinplate,  boxes, 
solder,  labels,  coal  and  labor. 

Unless  the  manufacturer  has  successfully  overcome  and 
mastered  all  of  the  principal  condensed  milk  defects,  and,  unless 
his  experience  justifies  him  in  believing  that  his  goods  will  stand 


194  MARKETS 

the  trials  of  storage,  he  will  find  it  advisable  not  to  manufacture 
more  than  he  can  promptly  dispose  of.  Even  at  best,  the  con- 
densed milk  will  be  from  three  to  six  months  old  before  it  is  all 
consum/ed,  and,  if  it  is  at  all  subject  to  deterioration,  the  sooner 
it  is  consumed  the  better. 

TRANSPORTATION. 

The  plain  condensed  bulk  milk  and  concentrated  milk  are 
highly  perishable  products.  If  shipped  considerable  distances 
they  should  be  placed  in  refrigerator  cars. 

The  evaporated  milk  and  sweetened  condensed  milk  in  her- 
metically sealed  cans,  and  the  latter  also  in  barrels,  can  safely 
be  shipped  in  ordinary  box  cars.  The  cases  weigh  from  fifty 
to  six-five  pounds,  and  the  barrels  from  three  hundred  to  seven 
hundred  pounds.  Care  should  be  taken  that  the  cars  used  for 
this  purpose  are  clean  and  did  not  previously  carry  goods  with 
strong  and  obnoxious  odors,  such  as  fertilizers,  as  these  odors 
are  prone  to  follow  the  condensed  milk  to  its  destination.  Strong 
box  cars,  in  good  repair  only,  should  be  used.  Even  at  best, 
the  cases  and  cans  suffer  more  or  less  damage  in  transportation. 
Cars  with  leaky  roofs  should  be  condemned,  as  transportation  in 
them  may  cause  the  package  to  suffer  in  appearance.  If  shipped 
on  steamboats,  it  should  be  specified  to  stow  the  cases  away  from 
the  boiler  room,  as  prolonged  exposure  to  high  temperatures 
causes  the  condensed  milk  to  deteriorate. 

CHAPTER    XVIII. 
MARKETS. 

A  large  proportion  of  the  canned  condensed  milk,  both 
sweetened  and  unsweetened,  supplies  localities,  territories  and 
countries  where  the  dairy  industry  is  yet  in  its  infancy,  or 
where  geographic  and  climatic  conditions  bar  the  profitable 
husbandry  of  the  dairy  cow.  Thus,  we  find  some  of  the  best 
condensed  milk  markets  in  the  tropics,  in  the  arctic  regions,  in 
the  army  and  navy,  on  ocean  liners  and  in  mining  and  lumber 
camps.  In  these  markets  condensed  milk  has,  in  many  cases, 
become  as  great  a  necessity  as  fresh  milk  is  to  the  inhabitants 
within  the  temperate  zone.  The  wastage  and  the  decreased 


MARKETS 


195 


production  of  diverse  food  products  caused  by  the  war  has 
opened  vast  new  markets  for,  and  has  caused  the  demand  and 
consumption  of  condensed  milk  to  grow  by  leaps  and  bounds. 
The  consumption  of  canned  condensed  milk  in  our  home  markets 
has,  also,  been  increasing  rapidly  \vithin  recent  years,  and  is 
today  assuming  astonishing  proportions.  This  increase  has  oc- 
curred, in  part  at  least,  at  the  expense  of  the  consumption  of 
fluid  milk.  While  conclusive  statistics  on  this  subject  are  not 
available,  the  trend  toward  larger  domestic  consumption  of  con- 
densed milk  accompanied  by  decreased  consumption  of  fluid  milk 
is  suggested  in  the  following  tables,  in  which  Prof.  J.  O.  Jordan,1 
President  of  the  International  Association  of  Dairy  and  Milk 
Inspectors,  shows  the  situation  in  the  city  of  Boston,  Mass. : 

Consumption  of  Condensed  Milk  in   Boston,   Mass. 


Source  of  Statistics 

Cases  pf  Condensed  Milk  by  Years 

1916 
Cases 

1917 
Cases 

1918 
Cases 

1919  * 
Cases 

Business  of  a  firm 
operating  chain 
stores  

30,500 
762,446 

52,700 
880,072 

76,500 
1,237,647 

77,000 
1,647,264 

Receipts  according 
to  records  of  Board 
of  Trade  

Daily  Consumption  of  Fluid   Milk  in   Boston,  Mass. 


Quarts    of    Milk 

which     should 

have    been    con- 

Year 

Quarts     of     Milk 
actually       c  o  n  - 
sumed  daily 

sumed     daily, 
based     on     esti- 
mated population 
and  quarts  used 

Estimated 
Population 

in   1916  by   esti- 

mate d  popula- 

tion 

1916     .  . 

347  735 

760400 

1917    

342  244 

353  209 

772  370 

1918    .. 

342451 

358617 

784  340 

1919*  

333506 

364  157 

796310 

1  Jordan,   Address,   Eighth   Annual   Convention   International   Association 
Dairy   and   Milk   Inspectors,    1919. 

*  1919  figures  are  for  ten  months  only.' 


196  MARKETS 

The  rapid  growth  of  the  ice  cream  industry  has  further 
developed  a  splendid  and  ever-increasing  market  for  plain  con- 
densed bulk  milk.  Additional  impetus  has  been  lent  this  devel- 
opment since  the  advent  of  national  prohibition,  which  caused 
a  vast  increase  in  the  consumption  of  ice  cream  and  of  soft 
drinks  of  which  ice  cream  constitutes  an  integral  part.  Manu- 
facturers of  condensed  milk  estimate  that  this  has  resulted  in 
an  increase  of  their  production  of  plain  condensed  bulk  milk 
amounting  to  from  15  to  20  per  cent. 

Market  Prices  of  Condensed  Milk. — The  price  of  condensed 
milk  is  not  controlled  by  the  general  market  of  dairy  products, 
nor  by  any  board  of  trade;  there  is  no  consistent  uniformity  of 
price  throughout  the  country  as  is  the  case  of  butter  and  cheese. 
The  price  of  condensed  milk  does  not  necessarily  follow  the 
rise  and  fall  of  the  butter  and  cheese  markets,  but  in  the  long- 
run  it  is  usually  affected  by  abrupt  fluctuations  of  prices  of  these 
other  dairy  products,  largely  on  account  of  the  influence  of  such 
fluctuations  on  the  supply  to  the  condensery  of  fresh  milk.  It 
is  chiefly  governed  by  local  conditions  of  supply  and  demand, 
conposition  of  product  and  reputation  of  the  individual  brand. 
Condensed  milk  is  sold  under  hundreds  of  different  brands  or 
labels.  While  one  and  the  same  concern  may  sell  scores  of 
different  brands,  the  brand  itself  has  very  little,  if  anything,  to 
do  with  the  quality  or  composition  of  the  contents  of  the  can. 
Each  brand  usually  sells  at  its  own  special  price,  although  the 
various  brands  put  on  the  market  by  the  same  concern  often 
contain  the  same  quality  of  milk  and  may  be  filled  with  con- 
densed milk  from  one  and  the  same  batch.  It  is  customary  in 
most  factories  to  fill  the  cans  before  they  are  labeled  and  the 
orders  for  different  brands  of  condensed  milk  are  filled  from 
the  same  general  stock.  The  brands  serve  largely  as  an  in- 
strument to  increase  the  sales  and  "dodge"  competitors. 

Sweetened  condensed  milk,  packed  in  hermetically  sealed 
cans,  sells  from  about  $3.25  to  $5  per  case  of  48  sixteen-ounce 
cans  and  the  cans  retail  at  from  5  to  20  cents  each,  according 
to  the  size  of  the  cans  and  market  conditions. 

Evaporated  milk,  unsweetened  condensed  milk  in  hermetic- 
ally sealed  cans,  sells  from  $2.25  to  $4.00  per  case,  according  to, 
the  size  of  the  cans  and  market  conditions. 


MARKETS  197 

Bu-lk  milk,  both  sweetened  and  unsweetened,  goes  direct 
from  the  manufacturer  to  the  purchaser  who  buys  it  at  prices 
agreed  upon  by  the  contracting  parties.  The  sweetened  con- 
densed milk  is  sold  in  barrels  holding  from  three  hundred  to 
seven  hundred  pounds  (usually  about  six  hundred  pounds)  to 
candy  and  caramel  factories,  bakeries  and  confectioners.  The 
price  varies  from  four  to  ten  cents  per  pound  according  to  the 
per  cent  of  fat,  demand  and  supply.  When  there  is  a  general 
"epidemic"  of  bad  canned  condensed  milk,  this  spoiled  con- 
densed milk  is  usually  turned  into  candy  shops  and  bakeries, 
where  it  is  sold  for  "a  song."  This  condition  has  always  a 
depressing  influence  on  the  price  of  sweetened  condensed  bulk 
milk,  which,  during  such  seasons,  may  have  to  be  sold  at  a  loss. 
Some  milk  condensing  concerns  operate  their  own  candy  shops 
which  take  care  of  the  condensed  milk  that  is  rejected  on  the 
market. 

Plain  or  unsweetened  condensed  milk  is  sold  in  1-gallon  to 
10-gallon  cans  to  ice  cream  factories,  the  price  varying  from 
twenty-five  to  ninety  cents  per  gallon,  according  to  fat  content, 
concentration  and  market  conditions.  The  market  for  this  class 
of  goods  is  not  very  constant,  but  the  profits  are  generally  high. 
It  reaches  ebbtide  in  winter  when  the  demand  for  ice  cream  is 
small.  Limited  quantities  of  plain  condensed  bulk  milk  are  also 
sold  in  milk  and  cream  bottles  for  direct  consumption.  The 
.concentrated  milk  finds  the  same  markets  as  the  plain  con- 
densed bulk  milk. 

The  above  range  of  prices  of  the  several  types  of  condensed 
milk  refer?  to  the  market  conditions  which  prevailed  while  the 
industry  was  protected  against  competition  with  goods  from 
abroad  by  an  import  tariff  of  2c  per  pound  or  $1.00  per  case  of 
condensed  milk,  and  to  conditions  prior  to  the  advent  of  the 
European  war  in  1914. 

In  1913,  the  United  States,  by  Act  of  Congress,  removed 
the  import  tariff,  placing  condensed  milk  on  the  free  list.  This 
Act  became  effective  in  the  fall  of  the  same  year.  Its  immediate 
effect  was  a  rapid  increase  in  the  importation  of  European  con- 
densed milk,  which  was  offered  for  sale  at  relatively  low  prices, 


198  MARKETS 

decreased  the  sale  of  domestic  goods  and  caused  the  holdings  of 
condensed  milk  to  accumulate  in  large  quantities.  Condensed 
milk  prices  depreciated  rapidly  throughout  1914  and  reached 
the  bottom  in  the  fall  of  that  year  when  financial  limitations 
compelled  many  concerns  to  move  their  goods  at  any  price.  At 
that  time  the  bottom  prices  of  condensed  milk  were  approxi- 
mately as  follows : 

Sweetened  condensed  milk  per  case. $2.50 

Evaporated  milk  per  case 1.90 

The  losses  suffered  by  this  slump  in  the  condensed  milk 
market,  caused  by  the  influx  of  cheap  foreign  goods  in  the 
absence  of  a  protective  tariff,  were  enormous  and  caused  bank- 
ruptcy of  numerous  of  the  financially  limited  concerns.  The 
outlook  for  the  future  of  the  industry  looked  very  uninviting 
at  best,  but  the  situation  was  saved  and  market  conditions 
reversed  by  the  urgent  food  requirements  of  the  Allied  nations 
in  the  European  war,  and  after  the  entrance  of  the  United  States 
into  the  war,  by  large  orders  for  the  American  army  and  navy. 

The  extraordinary  and  very  urgent  demand  for  condensed 
milk  by  the  U.  S.  Government  and  by  its  allies  during  the  war 
and  the  enormous  demand  for  exports  to  Europe  after  the 
armistice,  boosted  the  prices  of  this  product  to  a  level  not 
attained  since  the  Civil  War.  While  Government  regulations 
tended  to  hold  price  advances  within  reasonable  bounds  and 
while  lack  of  shipping  facilities  and  other  factors  caused  tem- 
porary fluctuations  downward,  the  price  advance  in  general  con- 
-tinued  until  the  spring  of  1919,  and  reached  the  following  maxi- 
mum figures  per  case: 

Sweetened  condensed  milk  per  case $9.25 

Evaporated  milk,  per  case. 6.50 

Exports  and  Imports. — Canned  condensed  milk  only  need 
be  considered  here. 

The  United  States  Bureau  of  Statistics  reports  the  following 
imports  and  exports  of  condensed  miilk  for  the  years  1911  to 
1919,  inclusive: 


EXPORTS  AND  IMPORTS  199 

Exports  and  Imports  of  Condensed  Milk  and  Evaporated  Milk 
for  the  Years   1911   to  1919,  inclusive.1 

Exports  Imports 


Years 

Pounds 

Dollars 

Pounds 

Dollars 

1911 

12,180,445 

936,105 

630,308 

46,088 

1912 

20,642,738 

1,651,879 

698,176 

61,671 

1913 

16,525,918 

1,432,848 

1,778,044 

135,724 

1914 

16,209,082 

1,341,140 

14,599,339 

1,089,440 

1915 

37,235,627 

3,066,642 

'33,624,189 

2,556,787 

1916 

159,577,620 

12,712,952 

18,174,505 

1,515,354 

1917 

259,102,213 

25,129,983 

18,375,698 

1,746,446 

1918 

553,439,554 

— 

29,926,931 

— 

1919 

852,275,264 

— 

16,509,239 

— 

Prior  to  1914  the  United  States  exported  condensed  milk 
chiefly  to  North  America,  Oceanica  and  Asia,  small  quantities 
were  also  exported  to  South  America,  Africa  and  Europe.  About 
60  per  cent  of  all  the  export  condensed  milk  went  to  countries 
of  the  North  American  Continent,  Canada  and  Panama  being 
the  leading-  markets.  During  the  last  few  years,  immediately 
preceding  the  world  war,  our  exports  to  Canada  had  fallen  off 
very  rapidly.  In  1911  the  exports  to  Canada  amounted  to  only 
about  15  per  cent  of  the  total  exports  of  condensed  milk  to  the 
same  country  in  1908.  The  rapid  development  of  the  milk  con- 
densing industry  in  Canada,  within  the  last  decade  was  largely 
responsible  for  this  situation.  From  1907  to  1911  there  was  an 
annual  decrease  in  the  total  exports  of  the  United  States.  In 
1907  they  amounted  to  $2,191,000.00  as  against  $936,105.00  in 
1911. 

Prior  to  1913,  the  imports  of  condensed  milk  into  the  United 
States  were  likewise  very  limited.  This  was  largely  due  to  the 
protective  tariff  on  imported  goods,  which  was  an  effective  agent 
to  exclude  foreign  brands  from  American  markets. 

In  the  fall  of  1913,  Condensed  Milk  was  placed  on  the  "free 
list."  This  resulted  in  an  immediate  and  rapidly  growing  in- 
flux of  condensed  milk  from  European  countries,  such  as  Switzer- 
land, Denmark,  Holland,  Sweden,  Norway,  Germany  and  Eng- 

1  United  States  Department  of  Commerce  and  Labor,  Bureau  of  Statistics 
for  1911  to  1919. 


200  CHEMICAL  COMPOSITION 

land.  At  first  the  bulk  of  the  influx  consisted  of  sweetened-. con- 
densed milk,  but  later  evaporated  milk  also  arrived  in  increas- 
ingly large  quantities,  causing  havoc  in  our  domestic  markets, 
and  an  almost  unprecedented  depression  in  the  industry  in  the 
Fall  of  1914.  At  the  same  time,  the  exports  further  decreased 
and  ceased  almost  entirely. 

In  1915  the  food  shortage  in  the  allied  countries  and  their 
need  of  condensed  milk  for  their  armies  and  navies  began  to 
counteract  the  effect  of  .the  removal  of  the  protective  tariff. 
Imports  decreased  while  large  and  repeated  contracts  for  exports 
to  the  Allies  brought  about  an  unprecedented  growth  of  our 
export  trade  of  condensed  milk  at  attractive  prices.  Our  exports 
were  further  increased  by  the  fact  that  the  war  deprived  non- 
combatant  countries  in  South  America,  Asia  and  Africa  of  their 
usual  imports  of  this  commodity  from  the  then  warring  coun- 
tries, opening  up  the  world  markets  to  the  United  States. 

The  exports  continued  to  increase  after  the  armistice  was 
declared,  the  volume  exported  being  limited  largely  only  by  the 
shortage  of  transatlantic  transportation  facilities.  After  the  first 
six  months  of  1919  the  increasingly  unfavorable  rate  of  exchange; 
of  foreign  moneys  commenced  to  make  itself  felt  and  since  then 
there  has  been  a  steady  decline  in  exports.  Early  in  1920  iso- 
lated shipments  of  condensed  milk  began  to  arrive  in  this  coun- 
try, foreign  manufacturers  being  attracted  by  and  taking  advan- 
tage of  the  high  exchange  value  of  the  American  dollar,  our  high 
domestic  prices  and  the  absence  of  tariff  on  condensed  milk 
imported  into  the  United  States. 

CHAPTER    XIX. 

CHEMICAL   COMPOSITION   AND   STANDARDS   OF 
CONDENSED    MILK. 

Sweetened  Condensed  Milk.— Sweetened  condensed  milk 
contains  all  the  constituents  of  fresh  milk  and  considerable  but 
varying  quantities  of  sucrose.  Its  composition,  therefore,  de- 
pends on  such  factors  as :  composition  of  the  fresh  milk  from 
which  it  is  made ;  the  degree  of  condensation  and  per  cent,  of 
cane  sugar  added.  As  all  of  these  factors  vary  in  milk  from 
Hifferent  localities,  and  in  milk  of  the  same  factory  at  different 


CHEMICAL  COMPOSITION  201 

seasons  of  the  year,  no  hard  and  fast  rule  can  be  given.  The 
following  figures  merely  show  the  average  composition  of  sweet- 
ened condensed  milk  as  obtained  from  the  results  of  analyses  of 
a"  large  number  of  different  brands. 

Average  Composition  of  Sweetened  Condensed  Milk. 

Water  26.5  per  cent. 

C  fat  9.0  per  cent,  ^j 

:,,Milk  solids  J    pr°teids  f  per  Cent     I    32.6  per  cent, 

milk  sugar        13.3  per  cent. 

L  ash  1.8  per  cent.  J 

Cane  sugar  40.9  per  cent. 

Total  100.0  per  cent. 

Water. — The  water  content  is  largely  governed  by  the  de- 
gree of  condensation  and  the  per  cent,  of  cane  sugar.  American 
brands  average  from  24  per  cent,  to  28  per  cent,  water.  In  ex- 
ceptional cases  milk  has  been  found  to  contain  as  low  as.  21  per 
cent,  and  as  high  as  34  per  cent,  water. 

Milk  Solids. — The  per  cent,  of  milk  solids  is  largely  gov- 
erned by  the  per  cent,  of  milk  solids  in  fresh  milk  and  the  degree 
of  condensation.  In  the  majority  of  brands  the  solids  fluctuate 
'between  28  and  34  per  cent. ;  in  extreme  cases  analyses  have 
shown  less  than  28  per  cent,  and  as  high  as  40  per  cent,  milk 
solids.  The  relative  proportion  in  which  the  various  solid  con- 
stituents are  present  is  the  same  as  that  in  the  fresh  milk  from 
which  the  condensed  milk  is  made,  provided  that  the  fresh  milk 
was  not  skimmed  previous  to  condensing. 

The  fact  that  the  U.  S.  standard  requires  not  less  than  28 
per  cent,  milk  solids  and  the  introduction  of  perfected  methods  of 
standardizing  have  an  unmistakable  tendency  toward  keeping 
the  percentage  of  milk  solids  down  to  28  per  cent. 

Butter  Fat. — The  butter  fat  in  sweetened  condensed  whole 
milk  fluctuates  from  about  8  to  12  per  cent,,  according  to  locality, 
season  of  year  and  degree  .of  condensation.  Sweetened  cog- 
jdensed  milk  sold  in  barrels  is  usually  partly  or  wholly  skimmed 
and  is,  therefore,  low  in  fat.  It  has  been  suggested  tliat  ;arr-small 
portion  of  trie  milk  fat  is  lost  during  the  process  of  condensation. 


202  CHEMICAL  COMPOSITION 

and  this  theory  is  frequently  resorted  to  by  condensed  milk  men 
to  explain  why  their  milk  is  low  in  fat.  It  has  been  claimed  by 
some  that  the  volatile  fats  (volatile  fatty  acids)  are  lost  during 
the  process  of  condensation.  This  claim  is  not  well  founded, 
since  repeated  experiments1  have  conclusively  demonstrated  that 
condensed  milk  contains  the  normal  amount  of  volatile  fatty 
acids.  It  has  further  been  experimentally  proven  that  the  con- 
densed milk,  when  made  properly  and  from  whole  milk,  contains 
fat  equal  in  amount  to  that  found  in  the  fresh  milk  used.  A 
reasonable  allowance  should  be  made,  however,  for  loss  of  milk 
due  to  spilling  and  wasting  in  pipes  and  retainers.  Experience 
has  shown  that  this  loss  amounts  to  about  fifty  to  one  hundred 
pounds  of  milk  per  average  batch  under  normal  conditions. 

Proteids. — The  per  cent,  of  proteids  in  the  condensed  milk 
varies  with  the  per  cent,  of  proteids  in  the  original  milk  and 
the  degree'  of  concentration.  It  fluctuates  usually  between  7.5 
and  9  per  cent.  The  heating  previous  to  condensing  coagu- 
lates a  portion  of  the  milk  albumin  and  alters  the  casein  to  the 
extent  that  it  is  not  precipitated  in  the  normal, way,  when  rennet 
is  added  to  the  diluted  condensed  milk. 

While,  in  most  analyses  of  sweetened  condensed  milk,  the 
per  cent,  of  proteids  nearly  equals  that  found  in  the  fresh  milk 
multiplied  by  the  degree  of  concentration,  there  is  a  tendency 
toward  a  slight  loss  of  this  constituent  due  to  precipitation  in 
the  forewarmers. 

Milk  Sugar. — Sweetened  condensed  milk  contains  from 
about  12.5  to  15  per  cent,  of  milk  sugar,  the  amount  varying 
according  to  the  degree  of  concentration  and  per  cent,  of  milk 
sugar  in  the  fresh  milk.  The  milk  sugar  is  not  known  to  undergo 
any  material  changes  as  the  result  of  the  condensing  process.  If 
condensed  milk  is  recondensed,  it  assumes  a  darker  color  which 
is  largely  due  to  the  caramelizing  of  a  part  of  the  milk  sugar, 
caused  by  the  action  of  prolonged  exposure  to  heat.  The  milk 
sugar  in  condensed,  milk  crystallizes  very  readily  and  causes  the 
condensed  milk  to  become  sandy  and  settled.  Chemical  anal- 
yses of  this  sugar  sediment  show  that  it  consists  principally 
of  milk  sugar.  The  primary  cause  of  this  property  lies  in  the 

1  Hunziker  and  Spitzer,  Indiana  Agricultural  Experiment  Station  Bulletin 
No.  134,  1909. 


CHEMICAL  COMPOSITION  203 

fact  that  sweetened  condensed  milk  contains  so  little  water 
(about  26.5  per  cent.)  that  the  milk  sugar  is  present  in  the  form 
of  a  supersaturated  solution ;  therefore,  any  condition  which 
favors  sugar  crystallization  will  tend  to  produce  this  defect.1 
Milk  sugar  requires  from  five  to  six  times  its  weight  of  water 
at  ordinary  temperatures  for  complete  solution.  In  sweetened 
condensed  milk  the  milk  sugar  has  access  to  only  about  twice 
its  weight  of  water  (12.5  to  15  per  cent,  lactose  to  25  to  27  per 
cent,  water). 

Ash. — The  per  cent,  of  ash  is  largely  dependent  on  the 
degree  of  condensation.  It  usually  varies  from  1.5  to  2  per  cent. 
It  is  quite  constant  in  fresh  milk  (normal  fresh  milk  contains 
uniformly  about  .7  per  cent.  ash).  The  per  cent,  of  ash  in 
sweetened  condensed  milk  may  serve,  therefore,  as  a  reason-, 
ably  reliable  factor  in  determining  the  degree  of  condensation. 
The  heating  of  milk,  before  condensing,  precipitates  and  renders 
insoluble  a  portion  of  the  mineral  solids,  principally  the  lime 
salts. 

Sucrose.— The  purpose  of  the  presence  of  sucrose  in  this 
product  is  to  preserve  it.  Most  of  the  sweetened  condensed 
milk  on  the  market  contains  from  37  to  44  per  cent,  sucrose,  or 
cane  sugar.  Wider  variations,  however,  are  not  infrequent.  In 
some  cases  analyses  showed  as  low  as  30  per  cent,  and  in  others 
as  high  as  48  per  cent,  cane  sugar.  Cane  sugar  dissolves  in  one 
half  its  weight  of  Avater,  so  that  under  normal  conditions  there 
is  sufficient  water  in  the  condensed  milk  to  keep  the  sucrose  in 
solution.  The  amount  of  sucrose  in  milk  does  not  appreciably 
affect  the  power  of  the  milk  to  dissolve  milk  sugar,  nor  does 
the  per  cent,  of  lactose  present  materially  affect  the  power  of  the 
milk  to  dissolve  sucrose. 

When  the  sweetened  condensed  milk  has  a  concentration 
of  about  2.5:1,  the  manufacturer  usually  aims  to  have  it  contain 
about  40  per  cent,  sucrose.  When  it  is  condensed  sufficiently 
only  to  contain  28  per  cent,  milk  solids  it  is  necessary  to  add 
sufficient  sucrose  to  bring  the  percentage  of  sucrose  up  to  about 
44,  in  order  to  insure  the  necessary  keeping  quality. 

1  For  further  details  on  causes  of  settled  sweetened  condensed  milk  see 
Chapter  XXII. 


204 


CHEMICAL  COMPOSITION 


Specific  Gravity. — The  specific  gravity  of  sweetened  con- 
densed milk  falls  within  the  limits  of  1.24  to  1.35.  Foreign 
brands  average  somewhat  higher  in  specific  gravity  than  Amer- 
ican brands.  The  specific  gravity  of  sweetened  condensed  milk  is 
controlled  by  the  degree  of  condensation,  the  per  cent,  of  fat  and- 
the  per  cent,  of  cane  sugar.  Milk  condensed  at  the  ratio  of  about 
2.5  parts  of  fresh  milk  to  1  quart  of  condensed  milk  and  contain- 
ing about  9  per  cent,  fat  and  40  per  cent,  cane  sugar,  has  a  speci- 
fic gravity  of  about  from  1.28  to  1.29.  The  specific  gravity  of 
sweetened  condensed  skim  milk  may  go  as  high  as  1.35,  and,  if  it 
contains  an  excess  of  cane  sugar,  it  may  be  still  higher. 

Chemical  Analyses  of  Sweetened  Condensed  Milk  of  Eighteen 

Different  Brands. 


Brand 

Milk 
solids 
per 
cent. 

Water 
per 
cent. 

Pat 
per 

cent. 

Pro- 

teids 
per 
cent. 

Lac- 
tose 
per. 
cent. 

Ash 
per 
cent. 

Sucrose 
per 
cent. 

1  "Silver  Spoon" 
Hires'  Condensed  Milk  Co 

31  90 

28  68 

8  40 

9  12 

12  56 

1  91 

40  38 

3  "Eagle" 
Borden's  Condensed  Milk  Co.  —  ... 
a  "Reindeer* 
Truro  O'ondense'd  Milk  Co 

31.08 
31  23 

25.99 
27  33 

8.72 
9  56 

8.15 
8  32 

12.35 
13  42 

1.83 
1  80 

42.93 

41  44 

»  "Tip  Top" 
Bordens'  Condensed  Milk  Co;  
»  "Challenge" 
Borden's  Condensed  Milk  Co  r_ 

36.57 
31.74 

21.67 
24.84 

10.07 
8.23 

9.35 
8.57 

15.00 
13.  C2 

2.15 
1  92 

41.76 
43  42 

8  "Sweet  Clover" 
Mohawk  Condensed  Milk  Co 

32.84 

24  07 

9  31 

8^71 

12,95 

1  €7 

43  09 

»  "Arrow" 
Wisconsin  Condensed  Milk  Co  
«  "Blue  Bell" 
American  Condensed  Milk  Co\—  . 
3  "Bed  Cross" 
Mohawk  Condensed  Milk  Co. 

31.15 
35.56 
34,78 

26,83 
26.50 
27.14 

8.00 
.  5.31 
il.07 

8.49 
9.50 
7  92 

12.87 
14.80 
14  03 

1.79 
1,95 
1  76 

42.02 
37.94 
38  54 

3  "Rose" 
Borden's  Condensed  Milk  Co. 

30  82 

24  76 

8  88 

8  08 

12  07 

1  81 

tn  -rff 

*  "Magnolia" 
Borden's  Condensed  Milk  Co.      _    _ 

31.98 

26.32 

8  64 

7  84 

13  50 

2  00 

42  00' 

»  "Rustic" 
Michigan  Condensed  Milk  Co  
*  "Milk  Maid" 
Anglo-Swiss  Condensed  Milk  Co  
""Jubilee" 
Th«  Manitoba  Dairy  Co. 

30.00 
35.69 
29  40 

27.63 
25.65 
32  15 

8.60 
9.65 
9  62 

7.07 
8.78 
8  61 

W.flo 

15.17 
11  30 

1.73 
2.09 
1  85 

41.00 
38.66 
oa  AK' 

9  "Export" 
Baldwin  Condensed  Milk  Co...:  .. 

32.24 

26.69 

11  50 

8  50 

12  35 

1  80 

•  41  o7 

a  "Owl" 
CatfMa  Milk  Condensing  Co..  
a  "Nestle" 
Heriry  Nestle      ,.  .  . 

31.61 
32.91 

30.84 
28.04 

10.61 
8  06 

8.47 
7  68 

12.40 
15  23 

1.81 
1  94 

37.55 
39  05 

8  "Upper  Ten" 
U.  8.  Condensed  Milk  Co...  

33.65 

27.88 

8.80 

8.34 

14.66 

1.85 

3847 

1  Spitzer,  Indiana  Agricultural  Experiment  Station,   1910. 

2  McGill,  Inland  Rev.  Dept.,  Ottawa,  Bulletin  No.  144,  1908. 

8  Cochran,   Special   Report  of  Analysis   of  Condensed   Milks   and   Infants' 
Foods,  Pennsylvania  Dept.  of  Agriculture,   1905. 


CHEMICAI,  COMPOSITION  205 

Evaporated  Milk. — The  same  factors  which  control  the 
chemical  composition  of  sweetened  condensed  milk,  also  govern 
that  of  the  unsw'eetened  product,  with  the  exception  that  the 
cane  sugar  is  absent. 

The  following  figures  represent,  in  round  numbers,  the 
average  composition  of  evaporated  milk  as  obtained  from  anal- 
yses of  a  large  number  of  American  brands. 

Average   Composition  of   Evaporated   Milk 
Water  73  per  cent. 


Milk  solids 

r  fat 

I    proteids 
\lactose 
ash 

8.3  per  cent.^j 
7.5  per  cent.  { 
9.7  per  cent.  ( 
1.5  per  cent.  J 

*   27 

100  per  cent. 

The  chemical  and  physical  properties  of  the  various  ingre- 
dients in  unsweetened  condensed  milk  are  affected  to  a  greater 
extent  than  in  the  case  of  sweetened  condensed  milk.  This  is 
largely  due  to  exposure  of  the  evaporated  milk  to  high  tempera- 
tures in  the  sterilizer. 

Water  and  Solids  are  governed  by  the  degree  of  concentra- 
tion and  the  relative  per  cent,  of  the  same  constituents  in  the 
fresh  milk.  The  per  cent,  of  solids  admissible  in  evaporated  milk 
is  largely  dependent  on  the  chemical  and  physical  properties  of 
the  milk  and  the  sterilizing  temperatures  employed.  Excess 
in  solids  in  this  product  jeopardizes  its  marketable  properties, 
owing  to  the  tendency  of  the  proteids  to  form  hard  lumps  of 
curd  during'  the  sterilizing  process.  Evaporated  milk  very  low 
in  solids  tends  toward  the  separation  of  its  butter  fat  in  storage. 
Analyses  show  a  range  of  from  23  to  31  per  cent,  solids.  Since 
the  per  cent,  of  solids  necessary  and  possible  to  be  contained  in 
marketable  evaporated  milk,  largely  depends  on  the  properties 
of  milk,  and,  since  these  properties  again  are  principally  con- 
trolled by  locality,  season  of  year,  crop,  feed  and  weather  con- 
ditions and  the  quality  of  the  fresh  milk,  the  solids  in  milk  from 
any  given  season  of  the  year  may  vary  very  considerably.  In 
some  localities  and  at  certain  times  of  the  year  the  best  results 
may  be  obtained  with  evaporated  milk  containing  28  per  cent 


206 


CHEMICAL  COMPOSITION 


solids.  In  other  localities  it  may  be  difficult  at  certain  seasons 
of  the  year,  to  incorporate  more  than  24  per  cent,  solids  without 
injuring  or  destroying1  the  marketable  properties  of  the  product.1 

Butter  Fat. — The  fat  varies  with  the  per  cent,  of  fat  in  the 
fresh  milk  and  with  the  degree  of  concentration.  No  fat  is  lost 
during  the  process  of  condensing  and  sterilizing.2  It  has  been 
claimed  by  some  that  in  the  process -of  manufacture,  the  volatile 
fatty  acids  escape  and  that  the  evaporated  milk  therefore  con- 
tains less  fat  than  the  fresh  milk  from  which  it  is  made,  times 
the  degree  of  concentration.  If  this  were  true  the  loss  of  fat  in 
the  evaporated  milk  would  not  exceed  .25  of  1  per  cent.  But 
analyses  show  that  the  fat  in  the  evaporated  milk  is  entirely 
normal  in  composition  and  contains  the  same  proportion  of 
volatile  fatty  acids  as  the  fat  in  the  fresh  milk. 

The  Composition  of  Milk  Fats  in  Evaporated  Milk.2 


Date  of 
Manufacture 

Belchert 

Meissl 
Number 

Iodine 
Number 

Melting  Point  of 
Mixed  Fats 

Melting  Point  of 
Insoluble  Fatty 
Acids 

August    1908    .          .... 

28  48 

33  64 

33  3  degrees  C. 

41.0  degrees  C. 

29.52 

33.60 

33.4  degrees  C. 

41.2  degrees  C. 

In  the  evaporated  milk  there  is  a  strong  tendency  for  the 
fat  to  separate  out  during  storage  and  to  churn  in  transportation. 
This  is  largely  avoided  by  the  proper  adjustment  of  the  steriliz- 
ing process  and  by  use  of  the  homogenizer. 

Proteids. — The  proteids  vary .  with  the  per  cent,  of  total 
proteids  in  the  fresh  milk  and  the  degree  of  concentration. 
Similar  to  the  case  of  sweetened  condensed  milk,  there  is  a  ten- 
dency of  a  slight  loss  of  proteids  in  evaporated  milk  due  to 
mechanical  adhesion  of  a  part  of  the  precipitated  curd  to  the 
heating  surfaces  in  the  forewarmers  and  in  the  vacuum  pan. 

Most  of  the  coagulable  milk  albumin  is  precipitated.  Fresh 
milk  contains  about  .16  per  cent,  of  albumin  that  is  not  coagu- 
lable by  heat.3  The  relation  of  soluble  and  insoluble  curd  is 

1  Hunziker,    Indiana   Agricultural   Experiment   Station,    Twenty-first    An- 
nual Report,  1908,  pages  67-68. 

2  Hunziker  and  Spitzer,  Indiana  Agricultural  Experiment  Station,  Bulletin 
No.    134. 

*  Hunziker,  Indiana  Agricultural  Experiment  Station,  Bulletin  No.  143. 


CHEMICAL  COMPOSITION 


207 


shown  in  the  following  table  which  represents  analyses  of  dif- 
ferent brands  of  evaporated  milk: 

Soluble  and  Insoluble  Curd  in  Evaporated  Milk.1 


Brand 

Insoluble 
Curd 
Per  Cent. 

Soluble 
Albumin 
Per  Cent. 

Total 
Proteids 
Per  Cent. 

Gold  Milk 

8.44 

.46 

8.90 

Columbine        .  . 

7.41 

.49 

7.90 

Kvery  Day   

7.54 

.46 

8.0 

Gold  Milk  

7.37 

.33 

7.70 

Star  . 

7.86 

.30 

8.16 

Morning1  Glory  .... 

8.28 

.34 

8.62 

Carnation   

6.49 

.52 

6.91 

Beauty   

8.39 

.39 

8.78 

Van  Camp's 

7.52 

.42 

7.94 

Monarch   

6.77 

.52 

7.29 

Diadem   

7.06 

.42 

7.48 

Reindeer 

6.88 

.52 

7.40 

Wilson's   

6.89 

.49 

7.38 

Dundee   

7.21 

.44 

7.65 

Average  

7.436 

.429 

,   7.865 

The  above  figures  show  that,  in  the  evaporated  milk,  prac- 
tically all  of  the  coagulable  albumin  is  changed  to  insoluble  curd. 
The  brands  analysed  contained  evaporated  milk  condensed  at 
the  ratio  of  2  to  2.4  parts  of  fresh  milk  to  1  part  of  evaporated 
milk.  The  soluble  albumin  found  corresponds  with  the  albumin 
not:  coagulable  by  heat,  normally  found  in  fresh  milk,  times  the 
ratio  of  concentration. 

The  casein  is  largely  precipitated  by  the  sterilizing  heat, 
but  is  present  in  the  form  of  very  finely  divided  particles.  This 
is  due  to  the  mechanical  shaking  to  which  the  evaporated  milk 
is  subjected  in  the  sterilizer  and  in  the  shaker.  In  many  batches 
of  evaporated  milk  the  precipitation  of  the  casein  during  sterili- 
zation is  so  fine  that  the  product  is  perfectly  smooth  without 
shaking.  The  casein  in  evaporated  milk  does  not  respond  to  the 
action  of  rennet  as  does  the  casein  in  fresh  milk. 


1  Hunziker,   Indiana  Agricultural  Experiment  Station,  Bulletins  Nos.  134 
and  143. 


208  CHEMICAL  COMPOSITION 

Milk  Sugar. — The  milk  sugar  is  present  in  per  cent,  corre- 
sponding with  that  of  the  original  milk,  times  the  degree  of  con- 
centration. A  portion  of  it  has  undergone  oxidation  (carameli- 
zation)  due  to  the  high  sterilizing  temperatures.  It  gives  to  the 
evaporated  milk  a  yellow  to  light  brown  color.  The  higher  the 
.sterilizing  temperature,  and  the  longer  the  exposure  of  the  evapo- 
rated milk  to  this  heat,  the  darker  is  its  color. 

Ash. — The  mineral  constituents  also  are  present  in  nearly 
the  same  proportion  to  the  other  solids,  as  in  fresh  milk.  They 
are  largely  rendered  insoluble  by  the  sterilizing  process.  The 
lime  constituents  frequently  are  found  in  the'bottom  of  the  cans 
in  the  form  of  hard,  whitish,  insoluble  granules.  For  discussion 
of  relation  of  ash  constituents  to  stability  of  casein,  see  Chapter 
XXIII  on  "Lumpy  and  Curdy  Evaporated  Milk." 

Since  the  ash  in  normal  fresh  milk  is  practically  constant, 
averaging  about  .70  per  cent.,  the  per  cent,  of  ash  in  the  evapo- 
rated milk  is  frequently  used  as  a  factor  in  determining  the 
degree  of  concentration.  The  results  may,  however,  be  very 
misleading,  since,  when  the  ash  is  precipitated  in  the  form  of 
granules,  it  is  practically  impossible  to  mix  it  back  into  the  milk 
in  order  to  obtain  a  representative  sample  for  analysis. 

The  Specific  Gravity  ranges  from  1.05  to  1.08,  according  to 
the  degree  of  concentration  and  the  specific  gravity  of  the  origi- 
nal milk.  It  averages  about  1.065. 

Plain  Condensed  Bulk  Milk  is  of  very  varying  composition, 
depending  largely  on  the  degree  of  concentration  and  the  per 
cent,  of  fat  present.  It  is  usually  made  from  partly  or  wholly 
skimmed  milk  and  is  condensed  at  the  ratio  of  3  to  4  parts  of 
fresh  milk  to  1  part  of  condensed  milk.  The  same  fact  applies 
to  the  composition  of  concentrated  milk. 


CHEMICAL  COMPOSITION 


209 


Chemical  Analyses  of  Twenty-four  Different  Brands  of 
Evaporated  Milk.1 


Brand 

Solids 

Water 

Fat 

Curd 

Lac-~ 
tose 

Ash 

Total 

Gold  Milk  

29.25 

7075 

9.42 

8.44 

9.75 

1  54 

9990 

Columbine  .... 
Every  Day.  .  .  . 
Gold    Milk 

24.63 
26.20 
2718 

75.37 
73.80 
7282 

7.45 
8.07 
907 

7.41 
7.54 
7.39 

8.56 
9.10 
9.23 

1.36 
1.47 
1  49 

99.98 
100.15 
10000 

Star 

29.04 

7090 

8.35 

786 

10.37 

1  62 

9916 

Morning   Glory 
Carnation    .... 
Beauty    

31.08 
23.81 
28.38 

68.92 
76.19 
71.62 

10.48 
8.05 
8.47 

8.26 
6.49 
8.39 

10.47 
7.55 
9.94 

1.67 
1.24 
1.56 

99.82 
99.49 
99.98 

Van  Camp's  .  .  . 
Wilson's    
Monarch   . 

27.89 
25.23 
26.70 

72.11 
74.77 
7330 

8.69 
8.70 
8.09 

7.52 
6.53 
6.77 

9.66 
8.68 
10.35 

1.54 
.37 
44 

99.52 
100.05 
9995 

Diadem 

24.96 

7504 

8.16 

7.06 

7.92 

33 

99.51 

Reindeer    

26.66 

73.34 

8.08 

6.88 

10.21 

45 

9996 

Dundee    

27.04 

72.96 

8.73 

7.21 

9.36 

.48 

99.74 

Sundry  samples 
1 

2802 

71.98 

8.93 

7.68 

9.86 

61 

10006 

2 

31  90 

68.01 

968 

849 

11.88 

.69 

9975 

3... 

2601 

73.99 

8.18 

6.77 

9.24 

46 

9964 

4  

2733 

7267 

904 

6.93 

9.42 

.51 

9957 

5  

29.37 

70.63 

9.71 

7.34 

10.52 

.56 

99.76 

6 

21  12 

7888 

7.30 

5.78 

6.78 

.12 

9986 

7.. 

2325 

7675 

7.98 

6.19 

7.96 

.25 

10013 

8  

2548 

74.52 

868 

6.34 

8.67 

.35 

9956 

9.. 

26.62 

73.38 

9.20 

7.00 

9.18 

.37 

100.13 

1  Hunziker  and  Spitzer,  Indiana  Agricultural  Experiment  Station,  Bulletin 
No.  134,  1909. 


210  CHEMICAL  COMPOSITION 

Condensed  Milk  Standards. — Federal  condensed  milk  stand- 
ards were  first  assembled  in  connection  with  the  Federal  Food 
and  Drugs  Act,  passed  June,  1906,  and  which  went  in  force  Janu- 
ary 1,  1907.1  These  standards  provided  that  both,  sweetened 
condensed  milk  and  unsweetened  condensed  milk  shall  contain 
not  less  than  28  (twenty-eight)  per  cent  milk  solids,  of  which 
not  less  than  27.5  (twenty-seven  and  five-tenths)  per  cent,  shall 
be  milk  fat. 

These  standards  have  been  modified  repeatedly  since  their 
introduction.1. 2, 3  The  standards  which  have  superseded  them 
and  their  earlier  modifications,  and  which  are  now  in  force  are 
as  follows : 

"Sweetened  condensed  milk,  sweetened  evaporated  milk, 
sweetened  concentrated  milk,  is  the  product  resulting  from  the 
evaporation  of  a  considerable  portion  of  the  water  from  the 
whole,  fresh,  clean,  lacteal  secretion  obtained  by  the  complete 
milking  of  one  or  more  healthy  cows,  properly  fed  and  kept, 
excluding  that  obtained  within  fifteen  days  before  and  ten  days 
after  calving,  to  which  sugar  (sucrose)  has  been  added.  It  con- 
tains, all  tolerances  being  allowed  for,  not  less  than  twenty-eight 
per  cent.  (28%')  of  total  milk  solids,  and  not  less  than  eight  per 
cent.  ($%•)  of  milk  fat.3 

"Unsweetened  condensed  milk,  evaporated  milk,  concen- 
trated milk,  is  the  product  resulting  from  the  evaporation  of  a 
considerable  portion  of  the  water  from  the  whole,  fresh,  clean, 
lacteal  secretion  obtained  by  the  complete  milking  of  one  or  more 
healthy  cows,  properly  fed  and  kept,  excluding  that  obtained 
within  fifteen  days  before  and  ten  days  after  calving,  and  con- 
tains, all  tolerances  being  allowed  for,  not  less  than  twenty-five 
and  five-tenths  per  cent.  (25.5%)  of  total  solids  and  not  less  than 
seven  and  eight-tenths  per  cent.  (7.8%)  of  milk  fat.1 

"Sweetened  condensed  skimmed  milk,  sweetened  evaporated 
skimmed  milk,  sweetened  concentrated  skimmed  milk,  is  the 
product  resulting  from  the  evaporation  of  a  considerable  portion 
of  the  water  from  skimmed  milk  to  which  sugar  (sucrose)  has 

1U.  S.  Department  of  Agriculture,  Circular  No.  19;  also  Hunziker,  Purdue 
Bulletin  No.  143,  1910. 

2  U.  S.  Department  of  Agriculture,  Food  Inspection  Decisions  Nos.  131, 
1911;  8158,  1915;  «  170,  1917. 

8  U.  S.  Department  of  Agriculture,  Food  Inspection  Decision  No.  158, 
April  2,  1915. 


SANITARY  PURITY  211 

been  added.  It  contains,  all  tolerances  being  allowed  for,  not 
less  than  twenty-eight  per  cent.  (28%)  of  milk  solids.2 

"Unsweetened  condensed  skimmed  milk,  evaporated  skim- 
med milk,  concentrated  skimmed  milk,  is  the  product  resulting 
from  the  evaporation  of  a  considerable  portion  of  the  water  from 
skimmed  milk,  and  contains,  all  tolerances  being  allowed  for, 
not  less  than  twenty  per  cent.  (20%',)  of  milk  solids."  2 

Requirements  of  Condensed  Milk  for  Export  to  the  Allied 
Nations. — Condensed  milk  shall  contain  not  less  than  9.2  per 
cent,  butter  fat. 

In  order  to  meet  the1  high  butter  fat  requirement  in  con- 
densed milk  furnished  to  the  Allies,  American  condenseries  which 
receive  largely  low-testing  milk  are  compelled  to  reinforce  their 
product  with  butter  fat.  This  is  done  either  by  removing  a  por- 
tion of  the  skim  milk,  or  by  the  addition  to  the  milk  of  butter 
fat  in  the  form  of  cream  or  unsalted  butter. 

CHAPTER    XX. 

'SANITARY  PURITY,  DIGESTIBILITY  AND  VITAMINE 
PROPERTIES  OF  CONDENSED  MILK. 

Sanitary  Purity. — From  the  point -of  view  of  freedom  from 
pathogenic  and  other  harmful  micro-organisms,  most  forms  of 
condensed  milk  are  superior  to  the  average  market  milk.  In  the 
first  place,  the  manufacture  of  a  marketable  condensed  milk 
makes  essential  eternal  vigilance  in  the  control  of  the  quality  of 
the  fresh  milk.  It  is  safe  to  state  that  in  no  milk  plants  does 
the  quality  of  the  fresh  milk  accepted,  receive  more  careful  atten- 
tion and  average  higher  than  in  the  milk  condensery.  The  foun- 
dation of  the  condensed  product,  the  fresh  milk,  therefore,  is  of 
a  relatively  high  standard  of  purity. 

Again,  the  temperature  to  which  the  milk  is  subjected  is  suf- 
ficiently high  to  destroy  the  germs  of  practically  all  milk-borne 
diseases;  so  that,  unless  the  condensed  milk  becomes  infected 
with  patliogenic  germs  after  condensing  and  before  the  tin  cans 
are  hermetically  sealed,  practically  all  danger  from  disease  germs 
is  eliminated.  In  the  case  of  evaporated  milk  the  marketable 


2  U.    S.    Department   of    Agriculture,    Food    Inspection    Decision    No.    170, 
March    31,    1917. 


212  DlGKSTlBIUTY 

product  is  free  from  all  forms  of  germ  life.  The  only  exception 
to  this  rule  would  apply  to  concentrated  milk,  in  the  manufacture 
of  which  the  milk  is  not  heated  to  temperatures  detrimental  to 
the  life  of  bacteria. 

Digestibility. — In  this  discussion  of  the  digestibility  of  con- 
densed milk  it  is  assumed,  that  the  condensed  milk,  unless  used 
in  admixture  with  other  foods,  is  diluted  to  approximately  the 
consistency  of  normal  milk.  «If  consumed  as  a  drink,  similar  to 
milk  but  without  proper  dilution,  its  concentration,  and  con- 
sequent excessive  richness,  would  obviously  seriously  interfere 
with  digestion.  While  there  are  no  experimental  data  available 
concerning  the  digestibility  of  condensed  milk,  the  results  of 
feeding  experiments  with  heated,  pasteurized  or  sterilized  milk 
vs.  raw  milk,  may  furnish  a  logical  guide  as  to  the  dietetic  effect 
of  condensed  milk.  Milk  pasteurized  at  high  temperatures,  or 
sterilized,  may  be  considered  comparable,  as  far  as  the  effect  of 
heat  is  concerned,  to  condensed  milk. 

Doane  and  Price1  report  the  following  experimental  results : 
"Raw  milk  is  more  easily  digested  when  fed  to  calves  than  either 
pasteurized,  or  cooked  milk.  Contrary  to  theory^  cooked  milk, 
when  fed  to  the  calves  used  in  these  experiments,  caused  violent 
scouring  in  the  majority  of  trials.  A  majority  of  physicians  in 
charge  of  children's  hospitals  corresponded  with,  favored  the  use 
of  raw  milk  for  infants  when  the  milk  is  known  to  be  in  perfect 
condition,  but  favored  pasteurized  milk  under  ordinary  condi- 
tions. With  one  exception  all  the  physicians  corresponded  with, 
discouraged  the  use  of  cooked,  or  sterilized  milk  for  infant 
feeding." 

Rosenau*  states  that  " Comparative  observations  upon  in- 
fants under  the  same  conditions  show  that  they  flourish  quite  as 
well  upon  heated  milk  as  upon  raw  milk.  Laboratory  experi- 
ments as  well  as  clinical  observations  coincide  with  the  view, 
that  heated  milk  is  quite  as  digestible  as  raw  milk.  In  fact  it  is 
now  claimed  to  be  more  so.  Metabolism  experiments  indicate 
that  the  utilization  of  calcium  and  iron  in  the  body  is  more  com- 
plete in  children  fed  upon  boiled  cow's  milk,  than  in  those  fed 
upon  raw  cow's  milk. 

1  Doane  and  Price,  Maryland  Agricultural  Experiment  Station,  Bulletin 
No.  77,  1901. 

*  Rosenau,  United  States  Department  of  Agriculture,  Bureau  of  Animal 
Industry,  Circular  No.  153,  1910. 


DIGESTIBILITY  213 

Stutzer1  who  conducted  experiments  of  artificial  digestion 
reports  in  favor,  of  boiled  milk,  while  similar  investigations  made 
by  Ellenberger  and  Hofmeister2  showed  no  difference  in  the 
digestibility  between  raw  and  cooked  milk. 

Rodet3  who  experimented  with  dogs  noticed  a  slight  dif- 
ference in  favor  of  boiled  milk.  Bruning4  fed  dogs,  pigs,  rabbits, 
and  guinea  pigs  with  raw  and  sterilized  milk  and  reports  that 
all  results  were  in  favor  of  the  sterilized  milk.  Bruckler's5  ex- 
periments with  dogs  showed  that  the  animals  gained  more  in 
weight  on  sterilized  milk  than  on  raw  milk,  but-that  their  general 
health,  vigor  and  vitality  was  better  when  fed  raw  milk.  Variot0 
observed  no  difference  in  the  effect  on  infants  between  raw  and 
boiled  milk. 

The  foregoing  citations  suggest  that  our  knowledge  of  the 
digestibility  of  heated  or  boiled  milk  is  exceedingly  limited  and 
that  the  results  obtained  and  conclusions  drawn  by  the  various 
investigators  are  at  variance.  In  experiments  with  the  living 
organism,  and  confined  to  so  few  specimens  as  seems  to  have  been 
the  case  in  the  work  reported,  the  factors  of  individuality  and 
environment  are  a  constant  stumbling  block,  magnifying  the 
limit  of  experimental  error  and  weakening  the  conclusiveness  of 
the  results.  On  the  basis  of  our  present  knowledge  it  seems 
reasonable -to  conclude  that,  as  far  as  the  digestibility  of  its 
inherent  ingredients  is  concerned,  condensed  milk,  when  con- 
sumed in  properly  diluted  form,  varies  but  little,  if  any,  from 
raw  milk.  The  .absence  in  condensed  milk  of  ferments,  such  as 
enzymes,  which  are  destroyed  in  the  process  and  which  may 
assist  digestion,  may  be  considered  the  most  important  defect 
of  'condensed  milk  from  the  point  of  view  of  digestibility. 

In  the  case  of  sweetened  condensed  milk,  however,  the  nutri- 
tive ratio  of  the  normal  milk  is  decisively  disturbed  by  the  pres- 
ence of  large  quantities  of  sucrose.  Even  when  diluted  to  far 
beyond  the  composition  of  normal  and  original  fluid  milk,  the 


1  Stutzer,  Landw.  Versuchs-Stationen,  40,  p.  307. 

2  Ellenberger   &   Hofmeister,    Bericht    ueber   das   Veterinarwesen   Koenig- 
reich   Sachsen,   1890. 

3  Rodet,  Compt.  rend.  soc.  biol.,   48,  p.  555. 

4  Bruning,   Muenchner  Mediz.,  Wochenschrift,  No.   8,   1905. 
*  Bruning,  Zeitschrift  fuer  Tiermed,  10,  p.  110,  1906. 

5  Bruckler,  Jahrbuch  fuer  Kinderheilk,  66,  p.  343,  1907. 
«  Variot,  Comp.  rend.,  139,  p.  1002,   1904. 


214  DIGESTIBILITY 

per  cent  of  cane  sugar  is  still  high,  causing  the  nutritive  ratio 
of  such  milk  to  be  abnormally  wide  and  unbalanced.  The  carbo- 
hydrates are  present  far  in  excess  of  the  protein,  fat  and  ash. 
If  fed  to  infants  exclusively  and  for  a  prolonged  period  of  time, 
the  growing  organism  is  bound  to  suffer  from  malnutrition  and 
at  the  expense  of  muscular  development. 

Furthermore,  it  is  conceded  by  the  medical  profession  that 
sucrose  is  not  a  suitable  form  of  carbohydrates  for  infants.  It 
is  not  as  digestible  as  lactose,  it  changes  the  bacterial  flora  of  the 
intestines,  enhancing  the  development  of  butyric  acid  and  other 
gas-forming  and  putrefactive  germs  at  the  expense  of  Bacillus 
bifidus,  which  is  the  natural  inhabitant  of  the  intestine  in  normal, 
milk-fed  babies. 

Sweetened  condensed  milk  is  generally  highly  advertised  by 
the  manufacturer  as  a  suitable  food  for  babies;  it  is  frequently 
recommended  by  physicians  and  in  some  instances,  it  is  claimed 
to  have  agreed  with  babies  wrho  were  unable  to  take  care  of  milk 
in  any  other  form.  It  is  not  improbable  that  in  these  extremely 
isolated  cases  of  baby  feeding,  when  all  other  feeds  failed,  the 
true  virtue  attributed  to  the  sweetened  condensed  milk,  lay  in 
the  fact  that  the  mothers  carefully  followed  the  directions  on 
the  label  for  dilution.  The  directions  specify  that  the  condensed 
milk  be  diluted  with  ten  to  sixteen  parts  of  water.  The  majority 
of  cases  of  digestive  disorders  in  bottle-fed  babies  are  undoubt- 
edly the  result  of  the  natural  tendency  of  the  mother  to  feed 
her  child  too  much  milk  or  too  rich  milk.  When  we  consider 
that  the  ratio  of  concentration  in  sweetened  condensed  milk  is 
only  about  2.5  to  1,  it  is  obvious  that  a  dilution  of  10  or  16  to 
1  is  a  great  relief  to  the  over-taxed  digestive  organs  of  infants, 
previously  fed  on  milk  too  rich  for  normal  digestion.  The  inv 
mediate  change  of  the  health  and  disposition  of  these  babies  for 
the  better,  as  the  result  of  turning  from  a  prolonged  siege  of 
too  rich  food  to  the  very  dilute  condensed  milk,  is  therefore  not 
surprising. 

The  manufacturer  of  sweetened  condensed  milk  in  this  coun- 
try is  inclined  to  load  his  product  excessively  \vith  sucrose.  He 
does  this  largely  in  an  effort  to  increase  the  keeping  quality  and 
to  guard  against  development  of  fermentations  in  the  finished 
article  that  ruin  the  goods  for  the  market.  While  a  certain 


VITAMINS  PROPERTIES  215 

amount  of  sucrose  is  necessary  to  preserve  this  milk,  yet,  if  the 
product  is  manufactured  from  a  good  quality  of  fresh  milk,  as 
it  should  be,  and  when  the  proper  sanitary  conditions  are  main- 
tained in  all  departments  of  the  factory,  sixteen  pounds  of  cane 
sugar  per  one  hundred  pounds  of  fresh  milk  is  entirely  sufficient. 
He  should  bear  in  mind  that  sweetened  condensed  milk  is 
used  and  accepted  by  the  consumer  as  a  substitute  for  market 
milk,  and  it  is  the  manufacturer's  moral  duty  to  retain  in  this 
substitute  the  normal  properties  and  composition  of  the  product 
which  it  is  supposed  to  replace,  as  nearly  as  is  consistent  with 
the  production  of  a  wolesome  and  marketable  product. 

Vitamine  Properties. — Recent  discoveries  by  nutrition  ex- 
perts1, 2  have  revealed  and  conclusively  demonstrated  the  pres- 
ence of  vitamines,  or  chemically  unknown  substances  of  food 
origin,  that  are  essential  for  the  normal  performance  of  the 
function  of  animal  life.  Extensive  feeding  experiments  have 
shown,  that  before  complete  growth  can  occur  in  a  young  animal, 
or  for  prolonged  maintenance,  or  for  the  prevention  of  certain 
diseases,  the  diet,  besides  being  adequate  as  regards  its  content 
of  proteins,  carbohydrates,  fats  and  mineral  salts,  must  contain 
certain,  at  present  unidentified  accessory  substances,  popularly 
called  vitamines.  ' 

Hart  and  his  co-workers  enumerate  three  of  these  vitamine 
substances,  namely,  wtater-soluble  vitamines  or  antineuritic 
vitamines;  fat  soluble  vitamines  or  antixerophthalmic  vitamines; 
and  antiscorbutic  vitamines.  The  absence  in  the  diet  of  each, 
or  all  of  these  vitamine  substances  causes  stunting  of  growth 
and  the  development  of  certain  characteristic  diseases. 

Water-Soluble  Vitamine. — The  absence  of  this  vitamine  in 
the  diet  retards  and  stunts  growth  and  leads  to  such  diseases 
as  polyneuritis  and  beriberi  (paralysis).  The  water-soluble  vi- 
tamine is  present  in  a  variety  of  foods  and  constitutes  an  inherent 
part  of  the  non-fatty  portion  of  milk. 

Fat-Soluble  Vitamine. — The  absence  of  this  substance  in 
the  diet  retards  and  stunts  growth  and  leads  to  the  disease  of 
xerophthalmia  (an  eye  disease  culminating  in  blindness).  The 

1  McCollum,  The  Newer  Knowledge  of  Nutrition,  1918. 
8  Hart,   Steenbock  and  Smith,   Studies  of  Experimental   Scurvy,   Journal 
Biological  Chemical  Chemistry,  Vol.  XXXVIII,  No.  2,  1919. 


216  VITAMINS  PROPERTIES 

fat-soluble  vitamine  is  present  abundantly  in  a  very  limited  list 
of  foods,  namely,  in  butter  fat,  egg  fat,  cod  liver  oil,  the  fats  of 
the  vital  organs  and  in  the  leaves  of  plants.  It  is  not  contained 
in  ordinary  animal  fats  such  as  lard,  nor  in  any  of  the  vegetable 
fats. 

Antiscorbutic  Vitamine. — The  absence  of  this  vitamine  sub- 
stance in  the  diet  causes  the  development  of  scurvy  and  similar 
scorbutic  diseases  and  skin  diseases.  The  antiscorbutic  vitamine 
appears  to  be  present  in  many  foods,  similar  to  the  water- 
soluble  vitamine,  and  it  is  abundantlv  present  in  raw  milk. 

....-•••  w-:' 

Effect  of  Heat  Employed  in  the  Manufacture  of  Condensed 
Milk  on  These  Vitamines.— The  heat  to  which  condensed  milk 
.is  subjected  in  the  process  of  manufacture  does  not  rob  the  con- 
densed milk  of  the  water-soluble  and  fat-soluble  vitamines,  so 
far  as  our  knowledge,  based  on  data  now  available,  is  concerned. 
This  applies  to  all  kinds  of  condensed  and  evaporated  milk  made 
from  whole  milk.  From  the  standpoint  of  these  two  growth- 
promiOting  and  curative  vitamines,  all  forms  of  condensed  whole 
milk  are,  therefore,  equally  desirable  for  infant  feeding;,  for 
children  and  for  the  adult,  as  is  whole  milk. 

.    '  '/     ;'.'•••  •"  7  ::  t     -.'    .nj^T:)-".; 

On  the  other  hand,  skim  condensed  milk  is  n6t  a.  satisfactory 
food  for  the  growing  young.  It  lacks  the  indispensable  fat- 
soluble  accessory  and  unless  supplemented  by  egg  yolk,  cod 
liver  oil  or  butter,  its  consumption  by  the  young  in:,the  place,,  of 
whole  milk,  or  in  the  place  of  condensed  milk  made  from  whole 
milk,  will  prove  disastrous  to  the  growth  and  well-being  of  those 
who  are  restricted  to  such  a  diet. 

Nor  does  imitation  condensed  milk,  such  as  the  "Hebe" 
product,  in  which  the  butter  fat  has  been  replaced  by  a  vegetable 
fat,  supplement  the  lacking  fat-soluble  vitamine  substance.  The 
public  should  clearly  understand  that  in  milk  or  condensed  milk, 
there  is  no  substitute  for  butter  fat  and  when  the  butter  fat  is 
removed  the  product  no  longer  can  take  the  place  of  milk.  See 
also  "Addition  of  Artificial  Fats,"  Chapter  XXIV. 

The  antiscorbutic  vitamine,  on  the  other  hand  appears 
to  be  destroyed  in  the  process  of  manufacture  of  evaporated 
milk,  as  shown  by  Hart  in  experiments  with  guinea  pigs.  Part 
found  that  commercial  unsweetened  condensed  milk  -(meaning 


COST  OF  MANUFACTURE:  217 

evaporated  milk),  had  lost  its  antiscorbutic  properties  when 
used  in  quantities  equivalent  to  an  amount  of  raw  milk  wjhich 
would.s'prevent  scurvy  in  guinea  pigs  on  a  diet  of  rolled  oats 
and  /^Iried .  hay. 

Hart's  results  agree,  with  those  of  many  other  investiga- 
tors in  the  fact  that  the  exposure  of  milk  to  sterilizing  tempera- 
ture, deprives  the  product  of  its  antiscorbutic  properties.  On 
the  basis  of  these  facts  evaporated  milk  cannot  be  recommended 
as  an  exclusive  milk  diet  for  babies  and  children.  If  evapo- 
rated milk  must  be  used  for  infant  feeding,  some  antiscorbutic 
supplementary  food,  such  as  orange  juice,  should  be  fed  in  con- 
junction with  the  exclusive  use  of  evaporated  milk  or  similar 
heated  milk  product. 

To  what  extent  the  antiscorbutic  properties  of  milk  are 
preserved  or  destroyed  in  the  manufacture  of  sweetened  con- 
densed milk,  has  not  as  yet  been  experimentally  demonstrated. 
This  product  is  not  exposed  to  sterilizing  temperatures  and  yet 
it  is  heated  at  least  to  the  boiling  point.  The  safer  course  to 
follow  here,  too,  if  sweetened  condensed  milk  must  take  the 
place  of  normal  raw  or  pasteurized  milk,  is  to  feed  it  in  con- 
junction with  a  known  antiscorbutic  supplementary  food,  such 
as  orange  juice. 

CHAPTER    XXI. 
COST    OF    MANUFACTURE. 

.,.  General  Discussion. — The  cost  of  manufacture  varies,  in  a 
general  way,  with  the  organization  and  size  of  the  factory, 
capacity  of  machinery  and  the  amount  of  the  output.  These 
variations  are  further  modified  by  the  cost  of  available  labor, 
the  price  of  milk,  cane  sugar,  tin  cans,  box  shocks,  coal  and 
other  supplies,  etc. 

In  a  properly  organized  plant  the  cost  of  manufacture  per 
case  of  finished  product  decreases  with  the  increase  of  the  out- 
put, provided  that  the  capacity  of  the  machinery  is  sufficient  to 
take  care  of  such  increase.  When  the  plant  is  forced  beyond 
its  capacity,  the  factory  operates  at  a  disadvantage,  and  the 
extra  labor  and  possible  waste  and  losses  tend  to  increase  the 
cost  per  case.  When  the  output  drops  below  100  to  150  cases 


218  COST  OF  MANUFACTURE 

per  day,  profitable  manufacture  becomes  difficult,  the  overhead 
expense  is  out  of  proportion  with  the  business,  the  factory  can- 
not take  advantage  of  rebates  in  the  purchase  of  supplies,  the 
factory  labor  is  relatively  high,  because  skilled  men  have  to 
do  manual  labor,  and  occasional  losses  due  to  spoiled  goods 
devour  the  profits  of  a  comparatively  large  portion  of  the  entire 
output. 

The  price  of  milk  fluctuates  with  season  and  proximity  and 
strength  of  competing  markets.  The  pre-war  fluctuations  em- 
braced a  range  of  from  $1.00  to  $2.00  per  one  hundred  pounds  of 
fluid  milk,  or  twenty-five  to  fifty  cents  per  pound  of  butter  fat. 
Maximum  war  prices  and  post-war  prices  up  to  and  including 
January  1,  1920,  reached  the  figure  of  $4.17  per  100  pounds  of 
milk. 

Cane  sugar  varies  in  price  largely  with  the  season  and  with 
the  success  or  failure  of  the  sugar  cane  crop.  Sugar  prices 
usually  reach  their  climax  in  fall  and  their  minimum  price  in 
late  winter  or  early  spring.  Pre-war  variations  usually  fell 
within  the  limits  of  $4.00  and  $6.50  per  one  hundred  pounds  of 
sugar.  Since  the  war  and  up  to  January  1,  1920,  the  price  of 
sugar  has  risen  to  17  cents  per  pound. 

Tin  cans  vary  in  price  with  style  of  can  and  whether  made 
in  the  condensery  or  bought  from  a  can-making  concern.  Some 
factories  are  paying  more  or  less  heavy  royalties  for  the  priv- 
ilege of  using  certain  patents  of  cans.  Cans  intended  to  be 
sealed  without  the  use  of  solder,  but  which  are  guaranteed  to 
make  a  hermetical  seal,  are  generally  higher  in  price  than  those 
in  the  sealing  of  which  solder  is  used.  This  difference  in  price, 
however,  is  offset,  in  part  at  least,  by  the  cost  of  the  solder 
and  gasoline.  Cans  purchased  from  can-making  concerns  usually 
are  more  expensive  than  cans  manufactured  in  the  condensery. 
This  holds  true  only  where  the  tin-shop  of  the  condensery  is 
properly  equipped  and  efficiently  manned.  In  normal  times 
the  cost  of  cans  bought  from  can-making  concerns  is  about  45 
cents  per  case  of  14  ounce  cans  and  55  cents  per  case  of  talfl 
size  cans,  varying  somewhat  with  size  and  style  of  can;  when 
made  in  the  condensery  the  price  may  be  lowered  from  10  to 
20  per  cent.  January  1,  1920,  prices  for  cans  were  about  88  cents 


COST  OF  MANUFACTURE  219 

per  case  of  48  14-ounce  cans  and  about  99  cents  per  c"ase  of  48 
cans  for  tall-size  cans. 

The  cost  of  coal  varies  with  quality  and  locality.  Under 
average  conditions,  the  condensing  and  packing  of  one  pound 
of  fluid  milk  requires  about  three-tenths  of  a  pound  of  coal  or 
thirty  to  forty  pounds  per  case.  A  good  quality  of  "mine  run" 
can  be  laid  dow'n  at  the  factory  in  states  near  the  coal  region, 
like  Indiana  and  Illinois  for  about  $2.50  per  ton,  or  in  northern 
states,  like  Wisconsin,  for  about  $3.30  per  ton.  The  cost  of  coal 
per  case,  therefore,  may  vary  from  about  three  and  eight-tenths 
to  six  and  a  half  cents  per  case.  Where  natural  gas  or  refuse 
from  lumber  mills  is  available,  the  cost  of  fuel  may  be  reduced 
materially  by  the  use  of  these  substitutes  for  coal.  Maximum 
war  price  raised  the  cost  of  coal  to  about  9  cents  per  case. 

Solder  and  gasoline  for  sealing  the  cans  average  about  three 
and  a  half  cents  per  case.  The  price  of  solder  is  about  twenty- 
seven  cents  per  pound  and  the  solder  used  per  case  of  forty- 
eight  cans,  amounts  to  about  one-tenth  of  a  pound.  Maximum 
war  price  raised  it  to  about  7c  per  case. 

For  venthole  cans 'the  amount  of  solder  needed  is  from  .3 
to  .5  of  one  ounce  per  case,  making  the  cost  in  normal  times 
about  seven-tenths  of  one  cent  for  tall  size  cans. 

In  the  case  of  the  sanitary  can  and  other  cans  with  solder- 
less  seals  this  item  drops  out  entirely. 

The  labels  vary  in  price  according  to  quality  of  paper,  and 
elaborateness  of  printing.  The  average  cost  of  labels  is  about 
four  cents  per  case.  Maximum  war  price  about  8  cents  per  case. 

The  box  shooks  and  nails  per  case  cost  about  eight  to  ten 
cents.  January  1,  1920,  the  price  of  box  shooks  per  case  for  14 
ounce  cans  was  about  23  cents  and  per  case  for  tall  size  cans 
about  26  cents.  In  the  case  of  fibre  boxes  the  cost  per  case  is 
about  18  cents. 

The  factory  labor  for  pre-war  conditions  was  about  12  to 
15  cents  per  case  and  the  administration  expense  about  5  to 
10  cents  per  case,  varying  widely,  of  course,  with  the  type 
of  organization  and  volume  of  business.  January  1,  1920,  the 
factory  labor  was  about  20  to  25  cents  per  case  and  the  adminis- 
tration expense  about  10  cents  per  case. 


220  COST  OF  MANUFACTURE 

Under  pre-war  conditions  the  freight  and  other  transporta- 
tion ranged  from  about  10  to  25  cents  per  case  averaging  about 
12  to  15  cents.  January  1,  1920,  the  freight  and  other  transpor- 
tation charge?  would  average  35  cents  per  case. 

Before  the  war  the  investment  in  factory,  equipment  and 
operating  expense  for  a  plant  with  a  capacity  of  about  500  cases 
per  day  amounted  to  about  $75,000,  placing  the  interest  and 
insurance  at  about  3  cents  per  case.  January  1,  1920,  a  factory 
of  similar  capacity  would  involve  an  investment  in  building, 
equipment  and  operating  expense  of  about  $175,000,  placing  the 
interest  and  insurance  at  about  7  cents  per  case. 

The  selling  expense  varies  widely  ranging  from  less  than 
10  cents  to  20  cents  per  case. 

The  following  tabulated  summary  may  serve  to  bring  out 
the  approximate  relative  expense  per  case  of  sweetened  con- 
densed milk  and  evaporated  milk  more  clearly : 

Sweetened  Condensed  Milk. 

Cost  per  case  of  forty-eight  cans.    These  cans  weigh  14  ounces 

net  per  can  or  42  pounds  net  per  case.    They  are  known  in  the 

trade  as  14  ounce  cans. 

1913.  1920. 

105    Ibs.    milk    (concentration  Jan.  1. 

2.5 :1)    @  $1.50    $1.57    @  $  3.60    $3.78 

16.8  Ibs.  sugar  (16  Ibs.  per  100) @     5.00         .84     @  15.75       2.64 

Tin   cans   (sanitary)    45  .88 

Boxes    (wooden)    075  .23 

Labels    040  .05 

Coal    045  .09 

Factory  labor    15  .23 

Administration  expense    07  .10 

Freight    14  .35 

Selling  expense 10  .12 

Interest    and    insurance    on    investment 

and  on  operating  capital .     .03  .07 


Total  cost  per  case $3.51  $8.54 


COST  OF  MANUFACTURE;  221 

Evaporated  Milk. 

Cost  per  case  of  forty-eight  tall  size  cans,  weighing  forty-eight 

pounds  net. 

1913.  1920. 
Jan.  1. 

106   Ibs.   milk @  $1.50    $1.59  @  $3.60    $3.816 

Cans   (vent  hole) 55  .988 

Boxes  (wood)    075  .262 

Labels 04  .053 

Solder  and  gasoline  (vent  hole  cans)  .  . .      .007  .014 

Coal 045  ,                   .09 

Factory  labor    15  .23 

Administration  expense    07  .10 

Freight    14  .35 

Selling  expense 10  .12 

Interest    and    insurance    on    investment 

and  on  operating  capital 03  .07 


Total  cost  per  case $2.797  $6.093 


PART  V. 

CONDENSED  MILK  DEFECTS,  THEIR  CAUSES 
AND  PREVENTIONS 

CHAPTER    XXII. 

CLASSIFICATION    OF    DEFECTS. 

Many  are  the  defects  which  cause  condensed  milk  to  be 
rejected  on  the  market  and  numerous  are  the  avenues  that  may 
lead  to  the  manufacture  of  defective  milk.  The  milk  faults  may 
be  of  mechanical,  physical,  chemical,  or  bacteriological  origin,  or 
they  may  be  due  to  a  combination  of  two  or  more  of  these  forces. 
In  some  instances  the  defects  can  be  detected  in  milk  during;  or 
immediately  after  the  process,  in  which  case  they  may  be  rem- 
edied, or  their  recurrence  prevented.  But  more  often,  several 
weeks  may  pass  before  abnormalities  develop  and  before  the 
manufacturer  realizes  that  something  is  wrong  with  the  milk. 
In  the  meantime,  the  conditions  which  originally  produced  the 
milk  defect  may  have  so  changed,  that  it  is  exceedingly  difficult 
to  locate  the  seat  of  the  original  trouble. 

DEFECTIVE    SWEETENED    CONDENSED    MILK. 

The  following  are  the  chief  and  most  common  defects  of 
sweetened  condensed  milk: 

1.  Sandy,  rough  or  gritty 

2.  Settled 

3.  Thickened  and  cheesy 

4.  Lumpy,  white  or  yellow  buttons 

5.  Blown  or  fermented 

6.  Rancid 

7.  Putrid 

8.  Brown 

9.  Metallic. 


SWEETENED  CONDENSED  MILK  DEFECTS  223 

Sandy,  Rough  or  Gritty  Sweetened  Condensed  Milk. 

General  Description. — This  is  condensed  milk  in  which  a  por- 
tion of  the  milk  sugar  has  been  precipitated  in  the  form  <<f  large 
crystals,  the  size  of  the  crystals  depending  on  the  conditions 
causing  crystallization.  First-class  sweetened  condensed  milk 
is  smooth  and  velvety.  Such  mjilk  is  not  entirely  free  from  sugar 
crystals,  but  they  are  so  minute  in  size  that  they  do  not  rob  the 
condensed  milk  of  its  natural  smoothness.  In  sandy  or  gritty 
condensed  milk  the  crystals  are  very  numerous  and  large  enough 
to  grind  between  the  teeth,  similar  to  salt  crystals  in  gritty 
butter.  The  presence  of  these  crystals  is  also  noticeable  to  the 
naked  eye;  the  milk  looks  candied.. 

Causes  and  Prevention. — The  sugar  crystals  which  render 
the  condensed  milk  rough  and  sandy  consist  largely  of  milk 
sugar.  The  solubility  of  milk  sugar  is  relatively  low.  Milk 
sugar  requires  about  six  times  its  weight  of  water  at  ordinary 
temperature  for  complete  solution.  Condensed  milk  contains 
from  12.5  to  15  per  cent  milk  sugar  and  only  about  26.5  per  cent 
water.  The  ratio  of  milk  sugar  to  water  in  sweetened  con- 
densed milk,  therefore,  is  1  :2,  while  for  complete  solution  it 
should  be  1  :6.  The  milk  sugar  in  this  product  is  present  in  a' 
supersaturated  solution  and  any  condition  which  favors  sugar 
crystallization  strongly  tends  to  precipitate  this  milk  sugar, 
because  there  is  more  of  it  present  in  the  milk  than  the  available 
water  is  capable  of  readily  keeping  in  solution.  The  chief  factor 
that  prevents  the  milk  sugar  from  precipitating  very  badly  is 
the  great  viscosity  of  the  condensed  milk.  This  is  largely  due 
to  the  caseous  matter  and  the  cane  sugar. 

Cane  Sugar  Content. — It  has  been  argued  that  the  large 
amount  of  sucrose  which  sweetened  condensed  milk  contains, 
is  the  principal  cause  of  sandy  milk  and  of  sugar  sediment  in 
the  bottom  of  the  tin  cans,  and  that  a  reduction  in  the  amount 
of  sucrose  lessens  the  tendency  of  the  sugar  to  crystallize  and 
the  milk  to  become  sandy.  This  line  of  reasoning  is  erroneous. 
The  presence,  in  water,  of  sucrose  in  solution  does  not  materially 
lessen  the  power  of  the  water  to  dissolve  milk  sugar,  provided 
that  the  sucrose  solution  is  not  a  saturated  one.  Sweetened 
condensed  milk,  contains  about  35  to  45  per  cent  sucrose  and 


224  SWEETENED  CONDENSED  MILK  DEFECTS 

24  to  28  per  cent  water.  Sucrose  dissolves  in  one  half  its  weight 
of  water.  The  sweetened  condensed  milk  does  not,  therefore, 
contain  a  saturated  solution  of  sucrose. 

Incomplete  Solution  of  Sucrose. — If  the  finished  product  is 
to  be  smooth  and  free  from  sandiness,  it  is  essential  that  the 
sucrose  which  is  added  to  the  hot,  fresh  milk  be  thoroughly  dis- 
solved before  the  mixture  reaches  the  vacuum  pan.  Undissolved 
sugar  crystals  in  a  medium  as  highly  concentrated  as  sweetened 
condensed  milk  have  much  the  same  effect  in  a  physical  way,  as 
have  bacteria  in  fresh  milk  in  a  biological  way ;  they  multiply 
rapidly.  Therefore,  if  all  the  sugar  added  to  the  fluid  milk  is 
not  completely  dissolved,  the  undissolved  sugar  crystals  give 
rise  to  wholesale  precipitation  of  the  milk  sugar  in  this  product 
after  manufacture,  and  since  the  crystals  of  undissolved  cane  sugar 
are  relatively  large,  their  presence  also  gives  rise  to  the  formation 
of  milk  sugar  crystals  of  large  size.  Hence  the  sandy  condition  of 
the  condensed  milk.  Complete  solution  of  the  cane  sugar  can 
best  be  accomplished  by  heating  the  liquid,  milk  or  water,  in 
which  the  sugar  is  to  be  dissolved,  to  the  boiling  point  and  by 
boiling  the  mixture  for  several  minutes ;  or  by  placing  the  sugar 
on  a  large  wire  mesh  strainer  (about  eighty  meshes  to  the  inch) 
which  stretches  across  the  sugar  well  and  allowing  hot  milk  to 
run  over  this  sugar  in{o  the  well  below.  In  this  way  the  sugar 
crystals  must  dissolve  before  they  can  reach  the  sugar  well. 

One  of  the  safest  methods  of  insuring  complete  solution  of 
the  cane  sugar  is  to  dissolve  it  in  a  separate  kettle  in  a  sufficient 
quantity  of  boiling  water  (preferably  distilled  water)  and  boil- 
ing the  syrup  for  five  to  fifteen  minutes.  If  the  syrup  thus  made 
is  given  a  few  minutes  rest  it  should  become  perfectly  clear; 
by  its  clearness,  the  purity  of  the  sugar  can  also  be  observed. 
If  a  scum  forms  at  the  top  it  should  be  removed ;  then  the  hot 
sugar  syrup  is  drawn  into  the  pan.  Care  should  be  taken  that 
the  milk  already  condensing  in  the  pan  has  not  become  too  con- 
centrated, otherwise  sugar  crystallization  may  set  in.  It  is  ad- 
visable to  inject  the  sugar  syrup  gradually,  rather  than  to  wait 
until  nearly  all  the  milk  is  in  the  pan. 

Excessive  Chilling  in  the  Pan. — The  cause  of  grittiness  of 
condensed  milk  may  lie  in  the  pan  itself.  Where  the  water  used 
for  condensing  is  very  cold,  and  where  one  end  of  the  spray 


CONDENSED  MILK  DEFECTS  225 

pipe  in  the  condenser  is  very  close  to  the  goose  neck  of  the  pan, 
as  is  the  case  with  most  of  the  vacuum  pans  in  use,  which  are 
equipped  with  horizontal  spray  condenser,  the  chilling  of  the 
vapors  and  of  the  spray  of  milk  rising  from  the  pan  is  so 
sudden,  that  sugar  crystals  are  prone  to  form  in  the  spray  and 
along  the  walls  of  the  pan.  These  crystals  either  stick  to  the 
side  of  the  pan,  or  fall  back  into  the  milk  where  they  later  mul- 
tiply and  cause  the  milk  to  become  sugary.  Trouble  from  this 
source  can  be  avoided  by  either  raising  the  temperature  of  the 
water  that  goes  to  the  condenser  which  is,  however,  not  practical 
under  most  conditions,  or  by  closing  the  holes  in  that  portion  of 
the  spray  pipe  which  is  nearest  the  pan.  This  can  easily  be  done 
by  wrapping  a  piece  of  galvanized  iron  or  tinplate  around  the 
portion  of  the  spray  pipe  to  be  closed,  or  by  filling  the  holes 
with  solder,  or  by  replacing  the  old  spray  pipe  by  a  new  and 
shorter  one,  properly  constructed. 

Superheating  at  End  of  Batch. — Sometimes  the  manufac- 
turer is  persistently  troubled  with  the  apprearance  of  crystals  in 
the  condensed  milk  of  monstrous  size,  as  large  as  rice  kernels ; 
this  condition  arrives  usually  very  gradually.  During  the  first 
few  days  after  manufacture,  only  a  few  of  these  large  crystals 
may  appear  in  some  of  the  cans.  In  the  course  of  a  few  weeks, 
all  of  the  cans  may  contain  specimen  of  these  "rice  crystals" 
which  increase  in  number  until  the  entire  contents  of  the  cans 
are  one  mass  of  "rice  crystals,"  rendering  the  milk  unsalable. 
The  direct  causes  of  this  particular  kind  of  sugar  crystallization 
are  excessive  concentration  of  the  condensed  milk,  the  use  of 
too  much  steam  pressure  in  the  coils  and  jacket  when  condensa- 
tion is  near  completion,  delay  in  the  drawing  off  of  the  condensed 
milk  from  the  pan,  and  leaky  steam  valves  in  the  pipes  leading 
to  jacket  and  coils. 

Toward  the  end  of  the  condensing  process  the  milk  becomes 
heavy,  thick  and  syrupy,  and  boils  with  much  less  violence.  If, 
at  this  stage  of  the  process,  excessive  steam  pressure  is  used  in 
the  jacket  and  coils,  the  milk  is  superheated,  often  causing  the 
precipitation  of  "rice  crystals."  Again,  where  the  finished  con- 
densed milk  is  drawn  from  the  pan  very  slowly,  either  owing  to 
too  small  an  outlet  in  the  bottom  of  the  pan,  or  because  the  milk 
is  forced  to  run  through  a  strainer  attached  to  the  outlet,  or 


226  SWEETENED  CONDENSED  Miut  DEFECTS 

because  the  finished  condensed  milk  is  retained  in  the  pan  as 
the  result  of  an  accident,  in  all  of  these  cases  there  is  danger 
of  superheating,  and  therefore,  of  the  production  of  these  large 
crystals.  This  danger  is  especially  great,  where  the  valves  of 
the  steam  pipes  leading  to  the  jacket  and  coils  are  leaking,  as 
is  often  the  case.  The  avoidance  of  excessive  concentration  and 
the  removal  of  any  conditions  that  tend  to  expose  the  finished 
or  the  nearly  finished  condensed  milk  to  excessive  heat  will 
usually  prevent  further  trouble  of  this  sort. 

Experimental  results  by  C.  S.  Hudson,1  on  the  solubility 
and  crystallization  of  milk  sugar  also  show  that  milk  sugar 
crystals  of  large  size  were  obtained  by  evaporation  of  a  solution 
of  milk  sugar  at  95  degrees  C.  (203  degrees  F.). 

Excessive  Concentration. — 'In  as  much  as  the  initial  cause 
of  the  precipitation  of  a  portion  of  the  milk  sugar  which  leads  to 
the  production  of  sandy  condensed  milk  lies  in  the  fact  that  the 
milk  sugar  is  present  in  this  product  in  the  form  of  a  super- 
saturated solution,  it  is  obvious  that  the  clanger  of  sugar  crystal- 
lization and  sandiness  in  this  product  increases  with  the  increase 
in  concentration.  This  is  fully  borne  out  by  practical  experience. 
The  higher  the  ratio  of  concentration  the  more  difficult  it  be- 
comes to  manufacture  a  smooth  condensed  milk.  The  danger 
here  is  further  augmented  by  the  fact  that  in  the  very  highly 
concentrated  product  the  tendency  of  superheating  is  augmented. 
And  the  superheating  gives  rise  to  very  large  crystals  which 
render  the  product  exceedingly  coarse.  The  superheating  is 
due  to  the  increased  sluggishness  of  the  very  thick  condensed 
milk  in  the  pan,  it  ceases  to  boil  vigorously  enough  and  is  there- 
fore excessively  exposed  to  the  hot  coils.  It  is  further  due  to 
the  slowness  with  which  this  product  leaves  the  hot  pan. 

Improper  Cooling. — The  method  used  for  cooling  the  sweet- 
ened condensed  milk  after  it  leaves  the  vacuum  pan  is  another 
important  factor  determining  the  smoothness  or  grittiness  of  the 
finished  product.  The  chief  principles  involved  here  are  the 
rapidity  and  extent  of  cooling  and  the  amount  of  agitation  to 
which  the  condensed  milk  is  subjected. 

In  order  to  fully  appreciate  the  importance  of  strict  atten- 

1  Hudson,   The   Hydration   of   Milk   Sugar    in    Solution,    Jour.    Am.    Chem. 
Soc.,  Vol.  XXVI,  No.  9,  1904. 


SWEETENED  CONDENSED  MILK  DEFECTS  227 

tion  to  details  in  the  cooling  process  of  sweetened  condensed 
milk,  it  should  be  understood,  that  the  formation  of  large  sugar 
crystals  in  concentrated  solutions  is  enhanced  by  sudden  chilling 
and  by  excessive  agitation  of  these  solutions.  In  the  case  of 
cooling  in  10  gallon  cans  as  described  under  ''Cooling  of  Sweet- 
ened Condensed  Milk,"  Chapter  VI.,  the  sudden  and  irregular 
chilling  of  a  part  or  all  of  the  sweetened  condensed  milk  in 
the  cooling  cans  is  the  result  of  the  use  of  badly  dented  cans, 
poorly  fitting  paddles,  a  warped  condition  of  the  pivots  on  which 
the  cog  wheels  in  the  bottom  of  the  cooling  vat.  revolve,  too  cold 
water,  and  the  application  of  too  much  cold  water. 

The.  paddles  must  scrape  all  parts  of  the  sides  of  the  cans, 
from  top  to  bottom.  This  is  possible  only  when  the  cans  are 
intact  and  their  sides  are  smooth  and  free  from  indentations. 
The  paddles  must  be  adjusted  properly  so  that  their  edges  fit 
snugly  against  the  sides  of  the  cans,  they  must  be  firmly  fastened 
to  the  cross  bars  and  forced  against  the  sides  of  the  cans  by 
springs.  In  order  that  the  cans  may  run  true  they  must  properly 
fit  into  the  rim  of  the  cog  wheels  in  the  bottom  of  the  cooling 
vat  and  the  pivots  on  which  the  cog  Wheels  revolve  must  be  per- 
pendicular. If  the  pivots  are  warped,  the  cog  wheels  cannot 
run  true  and  the  cans  wobble:  this  causes  uneven  and  incom- 
plete scraping  of  the  sides  of  cans  by  the  paddles. 

The  water  in  the  cooling  vat  should  not  be  cold,  but  have 
a  temperature  of  about  90  degrees  F.  when  the  cans,  filled  with 
the  hot  condensed  milk,  are  set  into  the  vat.  The  cold  water 
should  flow  into  the  vat  slowly  and  be  evenly  distributed 
throughout  the  vat.  This  is  best  accomplished  by  the  installa- 
tion of  a  perforated  pipe  running  the  entire  length  of  the  vat. 
The  cooling  must  be  gradual.  See  also  "Excessive  Stirring." 

Excessive  Stirring. — The  cans  should  revolve  slowly.  Rapid 
revolution  causes  excessive  agitation  of  the  condensed  milk, 
which  stimulates  the  formation  of  crystals.  About  five  revolu- 
tions per  minute  is  satisfactory.  In  order  to  make  more  effective 
the  proper  scraping  of  the  cans  by  the  paddles  when  the  cans 
revolve  slowly,  it  is  advisable  to  install  two  paddles  in  each  can, 
touching  the  periphery  of  the  can  on  opposite  sides. 

When  the  milk  has  been  cooled  to  between  60  and  70  de- 


228  SWEETENED  CONDENSED  MILK  DEFECTS 

grees  F.,  the  water  should  be  drawn  from  the  cooling  vat,  or 
the  cans  should  be  removed  at  once. 

In  the  newer  method  of  cooling,  in  which  the  hot  condensed 
milk  is  forced  under  pressure  through  a  1J  to  1J  inch  coil  sub- 
merged in  a  tank  of  cold  water,  there  appears  to  be  a  happy 
relation  of  rapidity  of  cooling  and  type  of  agitation,  that  assists 
in  avoiding  the  formation  of  crystals  sufficiently  large  to  cause 
sandiness.  While  the  cooling  here  takes  place  with  relatively 
great  rapidity,  the  agitation  appears  to  be  such  as  to  prevent,  in 
a  large  measure,  the  production  of  excessively  large  crystals. 
If  this  cooled  condensed  milk,  leaving  the  cooling  coil,  is  sub- 
sequently further  subjected  to  slow  agitation  for  several  hours, 
the  formation  of  small  crystals  is  encouraged  and  the  preven- 
tion of  a  sandy  condition  of  the  product  is  facilitated.  For  de- 
tailed description  of  this  method  of  cooling  see  "Cooling  Sweet- 
ened Condensed  Milk,"  Chapter  VI. 

Warming  Up  of  Too  Cold  Condensed  Milk.— Finally,  if  the 
condensed  milk  is  cooled  to  too  low  a  temperature,  either  by 
mistake,  or  as  the  result  of  the  cans  of  cooled  milk  standing  in 
a  very  cold  room  over  night,  so  that  the  condensed  milk  is  too 
thick  to  run  through  the  filling  machine,  it  is  best  to  warm 
it  up  by  simply  allowing  it  to  stand  in  a  warm  room.  The  prac- 
tice of  setting  the  cans  back  into  the  cooling  tank  and  revolving 
them  in  warm  water  is  objectionable,  since  this  stirring  of  the 
milk,  while  it  is  warming,  seems  invariably  to  produce  whole- 
sale sugar  crystallization,  and  therefore,  causes  the  condensed 
milk  to  become  very  gritty.  (See  also  Settled  Condensed  Milk.) 

Settled  Sweetened  Condensed  Milk. 

General  Description. — By  the  term  "settled  milk"  the  con- 
densed milk  man  refers  to  condensed  milk  which  has  precipi- 
tated and  thrown  down  a  portion  of  its  sugar,  forming  a  deposit 
of  sugar  crystals  in  the  bottom  of  the  can  or  barrel.  This  de- 
posit may  vary  in  amount  from  a  very  thin  layer  to  a  layer  an 
inch  deep  or  more,  according  to  the  character  and  age  of  the 
milk.  The  nature  of  this  sediment  also  differs  in  different  cases 
of  settled  milk.  It  may  be  soft,  and  upon  stirring  may  mix  in 
and  dissolve  readily,  or  it  may  be  very  dry  and  hard,  in  which 
case  it  sticks  to  the  bottom  of  the  can  with  great  tenacity,  and 


SWEETENED  CONDENSED  MILK  DEFECTS  229 

can  be  removed  and  mixed  into  the  milk  with  difficulty  only. 
Like  gritty  milk,  settled  milk  is  a  very  common  condensed  milk 
defect.  Though  it  does  not  render  the  product  less  wholesome, 
it  is  an  undesirable  characteristic.  Such  milk  is  usually  rejected 
on  the  market  and  results  in  a  partial  loss  to  the  manufacturer. 

Causes  and  Prevention. — It  is  obvious,  for  reasons  above 
referred  to,  that  the  conditions  leading  up  .to  the  production  of 
settled  milk,  are  closely  related  to  those  that  cause  milk  to 
become  gritty.  Condensed  milk  cannot  drop  its  milk  sugar, 
unless  the  latter  is  present  in  the  form  of  crystals.  The  absence 
of  crystals  then,  means  that  condensed  milk  will  not  settle  but 
experience  has  shown  that  it  is  a  practical  impossibility  to  manu- 
facture sweetened  condensed  milk  which  contains  no  sugar  crys- 
tals. Sugar  crystals  are  always  present  in  it,  and  the  fact  that 
the  milk  is  not  sandy  or  gritty,  does  not  necessarily  mean  that 
it  will  not  settle.  Nevertheless,  the  removal  of  conditions  con- 
ducive of  sandy  or  gritty  milk,  diminishes  the  tendency  of  the 
formation  of  sugar  sedim,ent.  The  successful  and  uniform  pro- 
duction of  condensed  milk  that  does  not  settle,  however,  involves 
additional  conditions  that  are  not  controlled  by  the  factors 
causing  gritty  milk. 

Effect  of  Density  on  Sugar  Sediment. — One  of  the  chief  of 
these  conditions  is  the  density  of  the  condensed  milk.  The  thin- 
ner the  condensed  milk,  the  greater  the  difference  between  the 
specific  gravity  of  the  liquid  portion  and  that  of  the  sugar  crys- 
tals; therefore,  the  more  readily  will  the  crystals  sink  to  the 
bottom.  The  viscosity  of  thin  condensed  milk,  also,  is  less  than 
that  of  thick  milk,  offering  less  resistance  to  the  force  of  gravity 
of  the  crystals.  In  the  manufacture  of  sweetened  condensed 
milk  that  has  the  proper  density,  about  2.5  parts  of  fresh 
milk  are  condensed  into  one  part  of  condensed  milk.  If  the 
evaporation  is  stopped  sooner,  so  that  the  ratio  is  much  less  than 
2.5  to  1,  the  condensed  milk  is  usually  too  thin  to  hold  its  sugar 
crystals  in  suspension  unless  its  specific  gravity  and  viscosity 
are  increased  by  the  addition  of  more  sucrose. 

Effect  of  Fat  Content  on  Sugar  Sediment. — The  per  cent  of 
fat  in  milk,  also,  influences  the  specific  gravity  of  the  condensed 
mtilk,  and  therefore,  has  some  effect  on  the  settling  of  the  sugar 


230  SWEETENED  CONDENSED  MILK  DEFECTS 

crystals,  although  to  a  relatively  slight  degree.  Nevertheless, 
sweetened  condensed  skimmed  milk  will  settle  less  readily  than 
sweetened  condensed  whole  milk. 

Effect  of  Cane  Sugar  Content  on  Sugar  Sediment. — The  per 
cent  of  cane  sugar  materially  influences  the  specific  gravity  and 
viscosity  of  the  condensed  milk.  Milk  with  a  high  per  cent  of 
sucrose  is  heavier,  more  viscous  and  drops  its  sugar  crystals 
less  readily  than  milk  with  a  low  per  cent  of  sucrose. 

Turning  the  Cans  to  Prevent  Sugar  Sediment. — Concerns 
wrho  have  been  continually  troubled  with  settled  milk  often  resort 
to  the  practice  of  turning  their  cases  daily,  or  at  other  regular 
intervals.  This  keeps  the -precipitated  crystals  in  motion,  but 
it  does  not  prevent  the  settling  entirely.  Moreover,  milk  des- 
tined to  settle,  as  the  result  of  defects  in  the  process,  cannot 
be  prevented  from  dropping  its  crystals  after  it  leaves  the  fac- 
tory. Some  concerns  have  stooped  to  printing  on  their  labels 
statements  similar  to  the  following:  "A  sediment  in  the  bottom 
of  this  can  indicates  that  this  condensed  milk  is  absolutely  pure 
and  free  from  harmful  ingredients."  Advice  of  the  above  de- 
nomination is  obviously  ridiculous  as  well  as  untrue. 

Adding  Powdered  Milk  Sugar. — It  has  been  explained  that 
after  the  condensed  milk  is  cooled  it  contains  sugar  crystals.  If 
those  crystals  are  large,  their  cubic  content  is  relatively  great 
in  proportion  to  their  surface.  Their  buoyancy  is,  therefore, 
sufficient  to  overcome  the  resistance  of  the  surrounding  liquid 
and  they  will  drop  to  the  bottom,  forming  a  sediment.  If  these 
crystals  are  very  small  and  fine  they  are  not  objectionable  and 
they  usually  do  not  cause  settled  milk,  because  their  gravity 
force  is  insufficient  to  overcome  the  resistance  of  the  viscous 
syrup.  It  has  been  further  shown  that  the  size  of  the  sugar 
crystals  is  largely  determined  by  the  size  of  the  first  crystals 
present.  Experience  has  demonstrated  that  the  addition  to 
the  condensed  milk  before  cooling,  of  very  fine  sugar  crystals. 
such  as  powdered  miilk  sugar  contains,  encourages  the  formation 
of  very  small  crystals  and  tends  to  guard  against  the  develop- 
ment of  large  and  coarse  crystals  during  subsequent  cooling. 
Hence  sugar  sediment  may  be  greatly  minimized,  if  not  entirely 
prevented,  by  adding  to  the  hot  sweetened  condensed  milk,  a 
small  amount  of  powdered  milk  sugar,  at  the  rate  of  a  tea- 


SWEETENED  CONDENSED  MILK  DEFECTS  231 

spoon  full  of  milk  sugar  per  one  hundred  pounds  of  condensed 
milk.  The  milk  sugar  must  be  added  as  soon  as  the  condensed 
milk  comes  from  the  pan,  if  the  milk  is  allowed  to  cool  before 
the  milk  sugar  is  added,  its  effectiviness  is  largely  lost. 

In  order  to  insure  the  full  desired  action  of  the  added  pow- 
dered milk  sugar,  this  powder  must  be  transferred  to  the  con- 
densed milk  in  such  a  manner  as  to  prevent  its  formation  into 
lumps.  It  must  be  evenly  and  finely  distributed  over  and  in  the 
condensed  milk.  The  use  of  a  flour  sifter  has  been  found  most 
suitable  for  this  purpose. 

Thickened  and  Cheesy  Sweetened  Condensed  Milk. 

General  Description. — The  term  "thickened  and  cheesy"  con- 
densed milk  applies  to  condensed  milk  that  has  become  thick 
and  in  some  cases  solid.  This  is  a  very  common  trouble  with 
milk  manufactured  in  late  spring  and  early  summer.  The  milk 
thickens  soon  after  its  manufacture  and  continues  thickening 
until  it  assumes  the  consistency  of  soft  cheese,  without  the  de- 
velopment of  acid.  In  this  condition  it  usually  has  a  peculiar 
stale  and  cheesy  flavor,  disagreeable  to  the  palate.  Such  milk  is 
invariably  rejected  on  the  market. 

Causes  and  Prevention :  Effect  of  Colostrum  on  Thickening. 
—It  has  been  suggested  that  this  spontaneous  thickening  is  due 
to  the  presence  in  the  fresh  milk  of  colostrum  milk,  because  this 
defect  appears  at  a  time  when  the  majority  of  the  cows  supply- 
ing the  condensery  freshen.  This  explanation  can  hardly  be 
considered  correct  and  there  is  no  experimental  evidence  avail- 
able substantiating  it.  If  the  presence  of  colostrum  milk  were 
the  cause  of  it,  the  thickening  would  take  place  during  the 
process,  as  the  result  of  the  action  of  heat  on  the  albuminoids. 
This  is  not  the  case.  This  thickening  begins  some  days  and 
often  some  weeks  after  manufacture  and  increases  as  the  milk 
grows  older. 

Effect  of  Cow's  Feed  on  Thickening. — Again,  the  cause  of 
this  defect  has  been  attributed  to  the  change  in  feed,  the  cows 
being  turned  from  dry  to  succulent  feed  at  the  time  when  this 
tendency  of  the  condensed  milk  to  thicken  occurs.  There  is 
no  reliable  evidence,  however,  of  how  the  succulent  pasture 


232  SWEETENED  CONDENSED  MILK 

grasses  on  which  the  cows  feed  can  bring  about  this  thickening 
action  in  the  condensed  milk. 

Effect  of  Bacteria  on  Thickening. — A  third  and  far  more  rea- 
sonable explanation  is  that  this  thickening  is  the  result  of  a 
fermentation  process.  It  is  quite  probable  that  the  thickening 
of  sweetened  condensed  milk  is  closely  related  to  the  sweet- 
curdling  fermentation  in  fresh  milk.  The  sweet-curdling  of 
fresh  milk  is  a  fermentation  characteristic  of,  and  frequent  dur- 
ing late  spring  and  summer.  It  is  caused  by  certain  species  of 
bacteria  which  are  capable  of  producing  a  rennet-like  enzyme, 
which  has  the  power  to  curdle  milk  in  the  sweet  state.  These 
bacteria  are  known  to  be  closely  associated  with  dirt  and  filth, 
especially  from  the  feces,  and  gain  access  to  the  milk  usually 
on  the  farms  where  the  production  and  handling  of  milk  is  not 
accomplished  under  most  sanitary  conditions. 

It  is  further  known,  as  the  result  of  analyses  that,  in  spite 
of  the  large  per  cent  of  cane  sugar  which  sweetened  condensed 
milk  contains,  the  bacteria  in  it  increase  with  the  age  of  the 
milk.  The  thickening  of  the  sweetened  condensed  milk  in  early 
summer,  therefore,  very  probably  is  the  result  of  a  slow  curdling 
of  its  casein,  caused  by  enzymes  which  are  produced  by  bacteria. 
It  has  further  been  demonstrated  that  condensed  skim!  milk 
thickens  more  readily  than  condensed  whole  milk,  which  may  be 
explained  by  the  fact  that  condensed  milk  without  butter  fat 
represents  a  more  favorable  medium  for  bacterial  growth.  Fur- 
thermore, it  has  been  conclusively  demonstrated  by  the  writer 
and  others  that  the  addition  of  cane  sugar  to  condensed  milk, 
in  excess  of  that  present  in  normal  condensed  milk,  greatly 
retards  thickening.  This  fact  suggests  that  the  higher  per  cent 
of  sucrose  has  an  inhibiting  effect  on  the  enzyme-producing  bac- 
teria, and  perhaps,  on  the  action  of  the  enzyme  itself.  This 
condensed  milk  defect  can  be  prevented  entirely  by  using,  during 
the  summer  months,  eighteen  pounds  of  sucrose  per  one  hundred 
pounds  of  fresh  milk,  so  that  the  condensed  milk  contains  about 
45  per  cent  sucrose. 

Effect  of  Finishing  in  Pan  With  High  Steam  Pressure  on 
Thickening. — Abnormally  thick  condensed  milk  is  also  the  result 
of  overheating  the  condensed  milk  in  the  vacuum  pan  toward 
the  close  of  the  process.  The  batch  should  be  finished  with  low 


SWEETENED  CONDENSED  MILK  DEFECTS  233 

steam  pressure  in  the  jacket  and  coils,  not  to  exceed  five  pounds 
of  pressure,  and  the  milk  should  be  drawn  from  the  pan  at  once 
after  condensation  is  completed.  The  superheating  to  which 
the  condensed  milk  is  subjected  in  the  pan,  when  finishing  with 
a  high  steam  pressure  in  jacket  and  coils,  or  when  the  milk  is 
not  drawn  from  the  pan  promptly  when  the  vacuum  pump  is 
stopped,  or  when  an  effort  is  made  to  condense  to  a  very  high 
degree  of  .concentration,  is  almost  sure  to  cause  the  finished 
product  to  spontaneously  thicken  with  age  and  this  tendency 
is  especially  pronounced  in  the  spring  and  early  summer. 

Effect  of  Age  on  Thickening. — Finally,  all  sweetened  con- 
densed milk  has  a  tendency  to  thicken  with  age.  Exposure  to 
high  storage  temperature  (summer  heat)  hastens  this  action. 
The  rapidity  of  thickening  in  storage  increases  with  the  increase 
in  temperature.  This  tendency  is  very  much  reduced,  therefore, 
by  protecting  the  goods  from  high  temperatures  and  by  storing 
them  below  60  degrees  F.  (See  Chapter  XVII  on  "Storage,"  page 
191.) 

Lumpy  Sweetened  Condensed  Milk. 

General  Description. — Lumps  of  varying  denominations  are 
not  infrequently  found  in  sweetened  condensed  milk.  They  ma}\ 
be  soft  and  permeate  the  contents  of  the  can  throughout,  or  may 
appear  especially  in  the  form  of  a  "smear"  along  the  seams  of 
the  can ;  or  again,  they  may  float  on  the  surface,  in  which  case 
they  are  usually  hard  and  cheesy,  and  either  white  or  yellow  in 
color.  Their  presence  gives  the  contents  of  the  can  an  unsightly 
appearance  at  best,  and  in  many  cases,  they  spoil  its  flavor. 
They  naturally  suggest  to  the  consumer  that  something  is  wrong 
with  the  condensed  milk,  and  cause  him  to  reject  the  whole 
package. 

Causes  and  Prevention. — The  chief  causes  of  lumpy  con- 
densed milk  are:  poor  quality  of  fresh  milk,  unclean  pipes  in  fac- 
tory, milk  from  fresh  cows,  acid  flux  in  tin  cans,  and  unclean 
and  contaminated  tin  cans. 

Poor  Quality  of  Fresh  Milk  and  Unclean  Factory  Condi- 
tions.— Upon  opening  the  can  of  condensed  milk,  even  shortly 
after  it  is  filled,  the  lid  is  covered  with  large  and  small  lumps  and 
specks  sticking  to  the  tin,  presenting  a  very  uninviting  "appear- 


234  SWEETENED  CONDENSED  MILK  DEFECTS 

ance.  This  condition  can  usually  be  traced  back  to  a  poor  qual- 
ity of  fresh  milk,  containing  too  much  acid.  Very  often,  too,  the 
cause  lies  in  the  factory  itself,  where  it  is  due  to  lack  of  clean- 
liness. A  thorough  inspection  of  milk  pipes  and  pumps  generally 
shows  accumulations  of  remnants  of  milk  which  get  into  the 
milk  of  the  succeeding  batch.  Where  this  condition  exists,  it  is 
noticeable  that  the  first  batch  of  the  day  contains  more  specks 
and  lumps  than  the  succeeding  ones.  These  lumps  do  not,  as  a 
rule,  grow  larger  in  size  nor  increase  in  number  with  the  age  of 
the  condensed  milk,  but  they  injure -its  appearance  to  the  eye, 
and  certainly  cannot  add  to  the  wholesomeness  of  the  milk.  They 
might  easily  be  accompanied  by  the  formation  of  ptomains. 
A  more  rigid  inspection  of  all  the  fresh  milk  as  it  arrives  at  the 
factory  and  thorough  scouring  of  all  milk  tanks  and  milk  pumps: 
pipes  and  conveyors  usually  prevents  the  recurrence  of  this 
defect. 

Milk  from  Fresh  Cows. — During  early  spring  there  is  a 
strong  tendency  of  the  ja'cket  arid  coils  in  the  vacuum  pan  to 
become  coated  with  a  thick  layer  of  gelatinous  and  lumpy  milk. 
This  is  probably  due  to  the  fact  that  milk  during  these  months 
conies  largely  from  freshened  cows  and  may  contain  some  colos- 
trum milk  which  coagulates  when  subjected  to  heat,  or  that 
the  proteids  of  milk  from  these  fresh  cows  are  abnormally 
sensitive  to  heat.  This  thickened  material  usually  does  not  leave 
the  pan  until  most  of  the  condensed  milk  has  been  drawn  off. 
It,  therefore,  appears  in  the  last  one  or  two  cooling  cans.  If 
the  milk  in  these  cans  is  mixed  with  the  rest  of  the  condensed 
milk,  the  lumps  will  appear  again  in  the  tin  cans.  The  last  cans 
drawn  from  the  pan  should,  therefore,  be  kept  separate.  The 
contents  of  these  remnant  cans  may  be  redissolved  in  hot  water 
and  should  be  recondensed  in  a  succeeding  batch.  In  this  way 
the  manufacturer  sustains  practically  no  loss.  In  order  to  pre- 
vent these  lumps  from  getting  into  the  cooling  cans,  some  fac- 
tories attach  a  strainer  to  the  outlet  of  the  pan.  This  practice 
is  as  unnecessary,  as  it  is  damaging  to  the  milk  in  the  pan. 
The  straining  greatly  retards  the  removal  of  the  milk  from  the 
pan,  and  the  milk  is  held  in  the  hot  pan  so  long,  as  to  cause 
partial  superheating  which  is  otherwise  detrimental  to  its  quality. 


SWEETENED  CONDENSED  MILK  DEFECTS  235 

Comparative  Composition  of  Gelatinous  Coating  of  the  Jacket 

and  Coils  and  of  Normal  Condensed  Milk  of  the  Same 

Batch,  Made  April  23,  1908. 

Coating  of  Jacket  Normal  Condensed 

and  Coils  Milk 

Moisture                           24.76  per  cent  30.34  per  cent 

Lactose                             13.12  ,13.16 

Fat                                     9.50        "  7.44 

Curd                                  8.14  7.30 

Ash                                     1.42        "  1.80 

Acid                                     .33  .40 

Sucrose                             41.36        "  40.02 


98.63  per  cent  100.46  per  cent 

The  above  analyses  were  made  in  order  to  determine  the 
difference  in  chemical  composition  between  that  part  of  the  batch 
which,  in  the  spring  of  the  year,  forms  a  gelatinous  coating  oh 
the  jacket  and  coils  and  that  part  which  remains  normal.  The 
figures  do  not  show  as  great  a  difference,  as  the  physical  com- 
parison of  the  two  products  would  suggest.  Possibly  the  most 
significant  point  these  analyses  show  is  that,  while  the  proteids 
in  the  coating  are  higher,  the  ash  is  lower  than  in  the  normal 
condensed  milk. 

A  large  portion  of  the  ash  of  milk  is  present  in  chemical 
combination  with  the  casein,  which  does  not  curdle  by  heat, 
while  the  albumin,  which  is  coagulated  by  heat,  contains  only 
a  very  small  amount  of  ash.  Therefore,  the  fact  that  an  increase 
in  the  proteids  of  this  gelatinous  coating  is  accompanied  by  a 
decrease  in  the  ash  content,  would  suggest  that  the  proteids  of 
the  coating  of  the  jacket  and  coils  consist  of  more  albumin  and 
less  casein  than  the  proteids  of  the  normal  condensed  milk  of 
the  same  batch.  Since  this  coating  of  the  jacket  and  coils  occurs 
only  in  the  spring  of  the  year,  when  most  of  the  cows  freshen, 
it  is  reasonable  to  assume  that  this  coating  is  the  result  of  the 
acceptance  at  the  factory  of  milk  too  soon  after  calving  and 
which  contains  excessive  quantities  of  proteids  and  other  sub- 


236  SWEETENED  CONDENSED  MiiyK  DEFECTS 

stances   which   are   highly   sensitive   to   heat,   such   as   albumin, 
colostrum,   etc. 

Excess  of  Acid  in  Condensed  Milk  and  Acid  Flux  in  Tin 
Cans. — The  presence  in  the  condensed  milk  of  organic  and 
mineral  acids,  in  excess  of  the  amount  which  normal  fresh  milk 
contains,  is  conducive  of  the  formation  of  lumps. 

Excessive  amounts  of  acid  in  condensed  milk  may  be  the 
result  of  fermentations,  usually  due  to  a  poor  quality  of  sugar, 
or  of  the  use  of  acid  flux  in  the  making  and  sealing  of  the  tin 
cans.  Condensed  milk  that  shows  acid  or  gaseous  fermentation 
usually  contains  lumps.  The  acid  which  it  develops  as  the  result 
of  the  fermentation,  curdles  the  casein  with  which  it  comes  in 
contact. 

One  of  the  most  common  channels  through  which  condensed 
milk  may  become  contaminated  with  acid  mechanically,  is  the 
use  of  cans,  in  the  manufacture  and  sealing  of  which  acid  flux 
was  used.  The  acid  flux  generally  used  contains  zinc  chloride. 
The  flux  precedes  the  solder  and  some  of  it  is  bound  to  sweat 
through  the  seams  into  the  interior  of  the  cans.  This  type  of 
lumps  usually  has  a  pink  or  brownish-red  color,  especially  in  the 
case  of  considerable  quantities  of  acid  flux.  Zinc  chloride  is  a 
highly  poisonous  product  and  its  use  in  the  manufacture  of  tin 
cans,  which  are  intended  for  receptacles  of  human  food,  should 
be  prohibited  by  law.  Aside  from  its  injurious  effect  on  the 
health  and  life  of  the  consumer,  its  presence,  even  in  small  quan- 
tities in  condensed  milk,  is  a  detriment  to  its  market  value.  In 
such  cans  there  accumulate,  usully  along  the  seams,  lumps  and 
smeary  substances  which  have  been  found  to  consist  of  casinate 
of  zinc. 

Most  commercial  soldering  fluxes  consist  largely  of  zinc 
chloride  and  are  highly  acid,  although  many  of  these  are  adver- 
tised as  acid-free  fluxes.  In  order  to  avoid  the  appearance  in  con- 
densed milk  of  lumps  from  this  source,  cans  should  be  used,  in  the 
manufacture  of  which  a  strictly  acid-free  flux  is  used  and  which 
are  sealed  with  acid-free  flux.  Dry,  powdered  resin  or  resin 
dissolved  in  alcohol  or  gasoline  are  harmless  in  this  respect  and 
are  just  as  effective  fluxes,  as  acid  flux. 


CONDENSED  MII,K 


237 


Buttons  -in  Sweetened  Condensed  Milk. — Buttons,  as  known 
to  the  condensed  milk  manufacturer,  represent  a  type  of  lumps, 
different  from  those  previously  described.  Buttons  are  lumps 
of  curd  of  a  firm  and  cheesy  consistency.  They  usually  float  on 
top  of  the  condensed  milk  in  the  can  or  barrel.  They  are  suffi- 
ciently firm  units  so  they  can  be  readily  removed  and  washed 
free  from  the  condensed  milk.  They  are  of  varying  sizes, 
depending  on  the  age  of  the  condensed  milk  and  the  temperature 
at  which  it  was  stored.  The  older  the  milk  and  the  higher  the 


Tig.  81. 

Typical  buttons  of  different  sizes — All  signs  of  mold  have  disappeared 
Courtesy  of  L.  A.   Rogers,  U.  S.   Dairy  Division 

storage  temperature,  the  larger  the  buttons.  Most  of  the  but- 
tons are  about  one  half  inch  in  diameter  but  frequently  they 
are  of  sufficient  size  to  cover  the  entire  surface  of  milk  in  the  can. 

These  buttons  have  a  whitish-brown  to  yellowish  or  reddish- 
brown  appearance.  They  appear  in  old  sweetened  condensed 
milk  more  frequently  than  in  milk  that  has  been  in  storage  for  a 
short  time  only.  They  are  entirely  absent  in  freshly  made  con- 


238  SWEETENED  CONDENSED  MILK  DEFECTS 

densed  milk.  They  themselves  have,  and  they  give  the  con- 
densed milk,  a  cheesy,  stale  flavor  and  lend  the  entire  product 
an  unsightly  appearance.  They  depreciate  the  market  value  of 
sweetened  condensed  milk. 

Causes  of  Buttons. — Experience  has  demonstrated  that  but- 
tons are  most  prone  to  appear  in  stored  condensed  milk,  in  the 
packing  of  which  no  attention  was  given  to  sanitary  conditions 
in  the  factory  and  of  the  cans  or  barrels,  and  that  the  use  of 
clean  sterile  cans  and  barrels  and  a  high  standard  of  sanitation 
in  the  handling  of  the  product  before  packing  greatly  minimizes 
this  defect.  That  they  are  the  result  of  biological  action,  direct 
or  indirect,  is  fairly  obvious,  and  the  fact  that,  the  milk  during  the 
process  of  manufacture  is  heated  to  temperatures  destructive  to 
most  vegetative  types  of  germlife,  strongly  suggests,  that  they 
are  the  product  of  recontamination  of  the  finished  product. 

Rogers.  Dahlberg  and  Evans1  of  the  United  States  Dairy 
Division  investigated  the  causes  and  control  of  buttons  experi- 
mentally. They  found  that  the  buttons  are  caused  by  the  growth 
of  the  mold  Aspergillus  repens,  and  possibly  by  other  molds; 
that  the  development  of  the  mold  colony  is  restricted  by  the 
exhaustion  of  the  oxygen  in  the  can  or  barrel,  and  that  the  button 
itself  is  probably  due  to  enzyme  action,  continued  after  the 
death  of  the  mold. 

These  findings  corroborate  earlier  experimental  results  by 
the  author,  who  was  unable  to  develop  growing  mold  colonies 
in  normal  sweetened  condensed  milk  from  inoculations  with  full- 
grown  buttons. 

Rogers  and  his  co-workers  demonstrated  that  the  time  re- 
quired for  the  development  of  the  various  stages  resulting  in 
button  formation  varies  with  temperature,  amount  of  air  avail- 
able and  possibly  other  factors.  The  mold  colony  usually  ap- 
peared in  5  to  10  days.  Mold  growth  is  supposed  to  cease  in 
two  to  three  weeks  on  account  of  the  exhaustion  of  the  air.  In 
one  month  a  reddish-brown  discoloration  became  quite  evident 
and  at  the  end  of  two  months  the  button  had  usually  assumed 

1  L.  A.  Rogers,  A.  O.  Dahlberg  and  Alice  C.  Evans,  The  Cause  and  Control 
of  Buttons  in  Sweetened  Condensed  Milk,  Jour.  Dairy  Science,  Vol.  Ill,  No. 
2,  1920. 


SWEETENED  CONDENSED  MILK  DEFECTS 


239 


definite  form.    The  disintegration  of  the  mold  hyphae  (filament) 
proved  to  be  a  slow  process,  extending  over  5  to  6  months. 


Prevention  of  But- 
tons.— The  prevention 
or  control  of  hese  but- 
tons may  be  accom- 
plished by:  1.  exclu- 
sion of  contamination, 
2.  low  temperature.  3. 
exclusion  of  oxygen. 

Exclusion  of  Con- 
tamination.— -Contam- 
ination of  the  con- 
densed milk  with  but- 
ton-forming molds  is 
most  likely  to  occur 
during  the  cooling, 
holding  and  filling 
operations  and  as  the 
result  of  contaminated 
cans  and  barrels. 


rig-.  82. 

Button  in   growing1   state,   molds 
still  very  evident 

Courtesy  of  L.  A.  Rogers,  U.  S. 
Dairy  Division 


In  condenseries  where  the  milk  is  cooled  by  the  old  method 
— in  open  10-gallon  cans,  revolving  in  a  cold  water  tank  and 
stirred  with  wooden  paddles — it  is  not  difficult  to  understand 
the  reason  for  buttons.  In  this  system  the  condensed  milk  is 
exposed  to  the  air  for  hours,  the  10-gallon  cans  and  the  wooden 
paddles  are  never  sterile  and  are  an  almost  sure  source  of  con- 
tamination, unless  special  precautions  concerning  the  sanitary 
condition  of  equipment  and  of  the  air  are  observed. 

In  condenseries  which  use  the  continuous  plan  of  cooling 
and  holding  of  the  sweetened  condensed  milk,  the  product  is 
protected  against  the  atmosphere  of  the  factory  from  the  time 
it  leaves  the  vacuum  pan  until  it  enters  the  tin  cans,  and  if 
this  equipment  is  kept  clean  and  is  steamed  out  thoroughly 
before  use,  which  is  readily  and  quickly  done  with  this  type 
of  equipment,  contamination  .should  be  very  largely  eliminated 
and  buttons  guarded  against. 


240  SWEETENED  CONDENSED  MII,K  DEFECTS 

The  empty  tin  cans  in  many  of  the  plants  are  kept  under 
undesirable  conditions.  They  are  exposed  to  diverse  channels 
of  contamination  during  transportation  to  the  factory  and  dur- 
ing storage  in  the  factory.  If  these  contaminated  cans  are  sub- 
sequently filled  with  the  condensed  milk,  contamination  is  un- 
avoidable and  buttons  are  likely  to  follow. 

The  tin  cans  should  therefore  be  protected  against  avoidable 
contamination,  or  better  yet,  they  should  be  sterilized  before 
filling. 

A  practical  sterilizer  of  empty  cans  may  be  readily  devised 
by  permitting  the  cans  to  pass  bottom-side-up  over  a  series  of 
gas  -flames,  under  a  hood.  This  method  is  used  successfully 
in  some  of  the  European  condenseries  and  has  for  them  solved, 
in  a  large  measure,  the  prevention  of  buttons.  The  caps  and 
filling  machines  obviously  should  receive  such  treatment  as  to 
prevent  them  from  becoming  sources  of  contamination.  Barrels 
should  be  steamed  till  piping  hot  and  then  paraffined,  before 
filling. 

In  factories  with  wooden  floors  where  the  filling  and  sealing 
is  done,  the  danger  of  mold  contamination  is  much  greater  than 
in  the  case  of  concrete  floors. 

According  to  Thorn  and  Ayres1  the  spores  of  the  mold  Asper- 
gillus  repens,  as  well  as  of  most  other  common  molds,  are  killed 
in  30  minutes  at  140  degrees  P.  The  preheating  of  the  milk  in 
the  hot  wells,  which  is  done  at  180  degrees  to  200  degrees  P., 
and  again  evaporation  in  the  vacuum  pan  at  135  to  150  degrees 
P.  are,  therefore,  sufficient  to  destroy  any  mold  present  in  the 
original  milk,  so  that  the  cause  must  be  confined  very  largely 
to  contamination  after  the  finished  product  leaves  the  vac- 
uum pan. 

Low  Temperature. — The  growth  of  most  molds  is  retarded, 
if  not  entirely  inhibited  at  low  temperatures.  This  also  is  the 
case  with  the  button-forming  mold  Aspergillus  repens.  Rogers 
et  al.,  state  that  this  mold  grows  very  poorly  at  temperatures 
of  68  degrees  P.  or  below.  They  report  that  they  have  never 

1  Thorn  and  Ayres,  Effect   of  Pasteurization  on   Mold   Spores,   Jour.  Agr. 
Res.,  Vol.  VI,  153-166,   1916. 


SWEETENED  CONDENSED  MILK  DEFECTS 


241 


observed  buttons  on  condensed  milk  held  at  68  degrees  F.  or 
below.  These  temperature  limits  are  not  corroborated  by  exper- 
iments by  Hunziker,  nor  by  the  experience  of  the  manufacturer. 
In  commercial  manufacture,  the  storage  of  sweetened  condensed 
milk  at  68  degrees  F.  will  show  copious  button  formation,  if  such 
milk  contains  button-forming  spores.  Reasonably  sure  preven- 
tion of  buttons  may  be  secured  by  holding  the  sweetened  con- 
densed milk  at  about  50  degrees  F.  or  below. 

Exclusion   of   Oxygen. — Molds   need   air  for   their   life   and 
growth.    They  cannot  develop  in  the  absence  of  oxygen.  Accord- 


\ 


\ 


Tig.   83. 

lutton  development  tinder 
atmosperic   pressure 


Pig".   84. 

Absence   of  buttons  in  20-inch 
vacuum 


Courtesy  of  L.  A.  Rogers,  U.  S.  Dairy  Division 


ingly  Rogers  et  al.,  by  careful  experimenting,  found  that  by  seal- 
ing the  cans  under  a  vacuum  of  20  inches  or  more,  button-for- 
mation in  condensed  milk  contaminated  with  button-forming 
molds  could  be  entirely  prevented. 

It  is  probable  that  a  similar  effect,  if  practicable,  could  be 
accomplished  also  by  charging  the  cans  with  an  inert  gas  to  the 
exclusion  of  atmospheric  oxygen. 


242  SWEETENED  CONDENSED  MILK  DEFECTS 

Blown,  or  Fermented  Sweetened  Condensed  Milk. 

General  Description. — One  of  the  most  disastrous  troubles 
in  the  manufacture  of  sweetened  condensed  milk  is  the  appear- 
ance of  "swell  heads."  This  term  is  applied  to  cans  of  con- 
densed milk,  the  contents  of  which  have  undergone  gaseous  fer- 
mentation, the  resulting  pressure  causing  the  ends  of  the  cans 
to  bulge  or  swell,  and  frequently  to  burst  open  the  seams.  In 
the  case  of  barrel  goods,  the  pressure  may  cause  the  barrel  head 
to  blow  out.  This  gaseous  fermentation  is  usually,  though  not 
always,  accompanied  by  the  development  of  acid  and  the  for- 
mation of  lumps. 

This  fermented  milk  is  worthless  for  any  purpose  and  means 
a  total  loss  to  the  manufacturer.  The  loss  is  generally  aug- 
mented by  the  fact  that  this  trouble  does  not  become  noticeable 
at  once ;  its  development  requires  several  weeks,  so  that  large 
quantities  of  condensed  milk  may  have  been  manufactured  before 
it  is  apparent  that  the  milk  is  defective.  Some  of  the  goods  may 
have  reached  the  market  before  the  cans  begin  to  swell,  in  which 
case  the  reputation,  of  the  respective  brand  is  jeopardized.  In 
some  instances  entire  batches  show  this  defect,  while  in  others 
only  a  few  cans  or  cases  of  each  batch  are  blown. 

Causes  and  Prevention. — This  defect  may  be  brought  about 
through  various  channels.  In  most  cases  it  is  due  to  contamina- 
tion of  the  milk,  on  the  farm  or  in  the  factory,  with  specific 
micro-organisms  which  are  capable  of  fermenting  one  or  more 
of  its  ingredients,  in  spite  of  the  preservative  action  of  the 
sucrose;  or  the  condensed  milk  may  contain  highly  fermentable 
substances  such  as  glucose  or  invert  sugar,  so  that  the  germs 
normally  present  in  the  condensed  milk  become  active  and  pro- 
duce  gas ;  or  the  milk  may  not  be  condensed  to  a  sufficient  degree 
of  concentration,  or  may  not  contain  adequate  quantities  of 
sucrose,  to  render  it  immune  to  the  bacteria  normally  present. 
The  cans  may  also  bulge  without  bacterial  action,  as  the  result 
of  exposure  to  a  wide  range  of  temperatures,  causing  mechanical 
contraction  and  expansion  of  the  contents. 

Contamination  with  Specific,  Gas-Producing  Bacteria  and 
Yeast. — This  is -by  far  the  most  common  cause  of  blown  milk. 
While  the  micro-organisms  which,  under  normally  sanitary  pro- 


- 

/s    <Lx  i   — 


SWEETENED  CONDENSED 


duction  of  milk  and  factory  conditions,  gain  access  to  the  con- 
densed milk,  are  largely  inhibited  and  do  not  ferment  the  sweet-     t 
ened  condensed  milk,  there  are  certain  specific  forms  of  bacteria 
and  yeast  whose   growth  is   not   retarded   by   the   concentrated 
sugar  solution  of  this  product.     Contamination  of  the  condensed  /•> 
milk  with  these  specific  organisms  is  usually  the  result  of  highly 
unsanitary  conditions  in  the  handling  of  the  condensed  milk. 

The  products  of  fermentation  depend  on  the  particular  type 
and  species  of  micro-organisms  involved.  In  most  cases  the 
sucrose  is  the  chief  constituent  attacked,  but  the  lactose,  also, 
is  capable  of  gaseous  fermentation,  though  instances  of  lactose 
fermentation  in  sweetened  condensed  milk  are  not  common. 

The  gaseous  fermentation  of  lactose  is  largely  caused  by 
bacteria,  yeast  and  molds  which  contain  the  lactose-splitting 
enzyme  "lactase,"  which  has  the  pow'er  of  hydrolizing  the  lac- 
tose. While  the  species  of  organisms  which  cause  lactic  acid 
fermentation  from  lactose  are  very  numerous,  those  containing 
the  enzyme  lactase  and  thereby  causing"  gaseous  fermentation 
from  lactose,  are  less  frequent,  at  least,  as  far  as  their  access  to 
milk  and  condensed  milk  is  concerned.  It  is  generally  under- 
stood, though  not  experimentally  proven,  that  species  of  micro- 
organisms which  do  not  contain  the  enzyme  lactase  have  no 
gas-producing  action  on  lactose. 

The  great  majority  of  cases  of  gaseous  fermentation  of 
sweetened  condensed  milk  are  the  result  of  the  action  of  micro- 
organisms on  the  sucrose,  especially  those  which  contain  the 
enzyme  "invertase."  The  majority  of  yeasts  secrete  invertase 
and  ferment  sucrose,  producing  alcohol  and  carbon  dioxide  to 
the  same  extent  as  in  the  case  of  glucose  fermentations.  The 
process  is  considerably  slower,  however,  especially  at  the  start, 
owing  to  the  fact  that  inversion  of  the  sucrose  must  precede 
fermentation.  For  this  reason  gaseous  fermentations  of  sweet- 
ened condensed  milk  do  not  become  noticeable  until  the  product 
is  one  or  several  weeks  old. 

Contamination  with  Yeast  on  the  Farm. — In  most  cases  of 
yeast  fermentations  of  sweetened  condensed  milk,  the  source  of 
contamination  lies  in  the  factory.  While  such  contamination 
may  and  often  does  occur  on  the  farm,  the  yeast  cells,  though 
they  may  be  spore-bearing,  are  destroyed  by  the  heat  to  which 


244 


CONDSNS^D  MILK: 


the  fresh  milk  is  subjected  in  the  forewarmers  and  before  it 
reaches  the  vacuum  pan.  The  thermal  death  point  of  all  forms 
of  yeast  which  have  come  to  the  attention  of  the  writer  in  con- 
nection with  a  vast  number  of  investigations  of  fermented  con- 
densed milk  was  below  180  degrees  F.  If  all  the  milk  is  properly 
heated  in  the  forewarmers  to  190  degrees  F.  or  over,  there  is, 
therefore,  little  danger  of  fermented  milk,  caused  by  contamina- 
tion of  the  fresh  milk  on  the  farm  with  yeast.  If,  however,  the 
heating  is  incomplete,  or  if  some  of  the  milk  passes  into  the 
vacuum  pan  without  having  been  properly  heated,  there  is  dan- 
ger of  milk,  contaminated  with  these  yeasts,  to  result  in  fer- 
mented condensed  milk. 

Contamination  with  Yeast  in  the  Factory. — As  previously 
stated,   veast   fermentation   of   condensed   milk   can   almost   in- 


•$., 


\ 


Fig*.  85.    Gaseous  fermentation  in 
sweetened  condensed  milk1 


Fig-.  86.     Yeast  cells  causing 
gaseous  fermentation 

This  species  is  capable  of 
fermenting  sugar  solutions 
containing  85%  sucrose.1 


variably  be  traced  back  to  contamination  in  the  factory.  After 
the  milk  leaves  the  forewarmers,  or  hot  wells,  it  is  never  again 
heated  to  temperatures  high  enough  to  destroy  these  destructive 
yeast  cells.  The  channels  through  which  yeast  contamination 
may  occur  in  the  factory  are  many. 


1  Hunziker,  A  Study  of  the  Causes  of  Fermented   Sweetened  Condensed 
Milk,  1910. 


CONDENSED  Miuc  DEFECTS  245 

Contaminated  Sugar. — The  sucrose  itself  may  be  contam- 
inated with  yeast.  This  is  frequently  the  case  and  especially  so 
if  the  sugar  is  exposed  to  dampness,  and  if  flies,  bees,  ants  or 
cockroaches  have  access  to  it. 

Again,  the  sugar  may  reach  the  milk  through  a  sugar  chute. 
The  lower  end  of  the  chute  is  usually  located  directly  over  the 
steaming  milk  in  the  hot  well.  The  vapors  arising  from  below 
may  be  condensed  in  the  chute,  causing  its  inside  walls  to  be- 
come damp,  and  sugar  will  adhere  to  the  damp  surface,  forming 
a  crust.  If  the  crust  is  not  removed  daily,  its  contamination  with 
yeast  and  other  dangerous  micro-organisms  is  almost  inevitable 
and  whenever  this  crust  peels  off  and  drops  into  the  milk,  the 
contamination  may  be  carried  into  the  finished  product,  giving 
rise  to  gaseous  fermentation. 

Contaminated  Machinery  and  Milk  Conveyors. — Remnants 
of  milk  may  lodge  in  the  condenser,  in  the  vacuum  pan,  in  the 
pipes  conveying  the  milk  and^  condensed  milk,  in  the  cooling 
cans  or  coils,  in  the  supply  tank  of  the  filling  machine,  or  the 
filling  machine  itself.  These  remnants  are  all  subject  to  con- 
tamination and  may  become  the  source  of  fermented  condensed 
milk.  The  strictest  attention  to  scrupulous  cleanliness  and  con- 
tinuous inspection  of  all  parts  of  conveyors  and  apparatus  which 
come  in  contact  with  the  milk  are  the  only  consistent  safeguards 
against  trouble  from  this  source. 

Contamination  Through  "Cut-opens." — It  is  customary  to 
empty  the  contents  of  sample  cans  which  are  cut  open  for  any 
purpose,  back  into  the  condensed  milk  of  succeeding  batches.  If 
these  samples  happen  to  be  contaminated  wjth  the  fermenting 
germs,  the  defect  is  naturally  propagated  from  batch  to  batch 
and  it  is  exceedingly  difficult  to  locate  the  source  of  the  trouble. 
It  is  obvious  that  all  suspicious  "cut-opens"  should  be  rejected 
and  that  all  "cut-opens"  that  are  utilized  should  be  emptied  into 
the  hot  well  where  their  contents  are  boiled  up  again. 

Dangerous  Effect  of  Poor  Quality  of  Sugar. — Sweetened 
condensed  milk  is  not  sterile.  There  is  no  part  of  the  process 
that  would  render  it  sterile  and,  from  the  time  it  leaves  the 
vacuum  pan  to  the  time  when  the  tin  cans  are  hermetically 
sealed,  it  is  exposed  to  contamination  with  microbes,  even 


246  SWEETENED  CONDENSED  MILK  DEFECTS 

though  the  factory  observes  the  most  rigid  attention  to  scrupu- 
lous sanitation  and  cleanliness.  Most  of  these  microbes  are 
harmless  and  their  growth  is  inhibited  by  the  preservative  action 
of  the  cane  sugar.  If,  however,  a  poor  quality  of  sucrose  is  used, 
which  may  contain  traces  of  invert  sugar,  or  acid,  etc.,  many  of 
these  common  species  of  micro-organisms,  harmless  in.  normal 
condensed  milk,  find  an  opportunity  to  develop  and  cause  gase- 
ous fermentation.  The  presence  of  invert  sugar  makes  unneces- 
sary the  action  of  invertase  in  order  to  start  fermentation ;  thus, 
microbes  which  do  not  secrete  invertase  and  are  otherwise  harm- 
less, may  become  detrimental  in  the  presence  of  invert  sugar, 
added  to  the  milk  in  the  form  of  a  poor  quality  of  cane  sugar. 
In  a  similar  wtay  the  use  in  condensed  milk  of  commercial  glu- 
cose, as  a  substitute  of  a"  part  of  the  cane  sugar,  and  in  order  to 
reduce  the  cost  of  manufacture,  is  bound  to  cause  disastrous 
results.  Nothing  but  the  best  refined,  granulated  sucrose  should 
be  used,  the  best  is  the  cheapest 

Dangerous  Effect  of  High  Acid  in  Milk. — Acids  have  the 
power  of  inverting  sucrose.  The  inversion  by  acid  is  especially 
active  in  the  presence  of  heat.  The  milk  in  the  vacuum  pan  is 
condensing  at  130  to  150  degrees  F.  These  temperatures  are 
most  favorable  to  inversion  of  a  portion  of  the  sucrose  in  the 
presence  of  acid.  The  higher  the  acid  content  of  the  milk,  the 
more  active  is  the  inversion.  Since  invert  sugar  is  the  very 
ingredient  necessary  to  cause  bacterial  action  in  the  finished 
product,  it  is  essential  that  the  acidity  of  the  milk  to  be  con- 
densed, should  be  held  down  to  the  minimum  in  order  to  avoid 
trouble  from  this  source. 

Contamination  with  Butyric  Acid  Bacteria. — Frequently  the 
troublesome  microbe  is  not  a  yeast,  but  belongs  to  a  species  of 
bacteria  highly  resistant  to  heat,  and  which  fail  to  be  destroyed 
by  heating  the  milk  to  the  boiling  point.  In  this  case,  the  con- 
tamination usually  originates  on  the  farm.  Organisms  of  this 
kind,  which  infest  the  milk  on  the  farm  in  this  connection, 
largely  belong  to  the  butyric  acid  group.  The  most  prominent 
among  them  are  Granulobacillus  saccharo-butyricus  mobilis  or 
Bacillus  saccharobtttyricus,  Bacillus  esterificans,  Bacillus  dimor- 
phobutyricus.  The  putrefactive  forms  of  butyric  acid  organisms, 


SWEETENED  CONDENSED  MILK  DEFECTS  247 

such  as  Bacillus  putrificus,  Plectridium  foetidum,  Plectridium 
novum,  etc.,  do  not  seem  to  thrive  in  sweetened  condensed  milk. 

The  contamination  may  occur  from  dust  of  hay  and  other 
fodder,  grain,  bedding,  or  the  unclean  coat  of  the  udder  and  sur- 
rounding portions  of  the  animal,  or  from  milking  with  wet  and 
unclean  hands,  or  from  remnants  of  milk  in  unclean  utensils. 

It  is  noticeable  that  the  great  majority  of  cases  of  blown 
milk  appear  during  late  summer  and  early  fall,  when  the  crops 
are  harvested  and  the  air  in  the  barn  is  frequently  loaded  with 
dust  from  the  incoming  crops.  Gelatin  plates  exposed  in  the 
stable  before  and  during  the  filling  of  silos  showed  an  enormous 
increase  of  colonies  on  the  plates  exposed  during  the  filling  of  the 
silos,  s/ Milk  drawn  under  such  conditions  is  naturally  subjected 
to  excessive  contamination,  unless  special  precautions  are  ob- 
served. 

A  very  common  source  of  these  butyric  acid  organisms  also 
is  remnants  of  milk  in  pails,  strainers,  coolers,  cans  and  any 
other  utensils  with  which  the  milk  may  come  in  contact,  also 
polluted  water  used  for  rinsing  the  utensils.  The  cheese-cloth 
strainer,  owing  to  the  fact  that  it  is  difficult  to  thoroughly  clean 
and  that  it  is  very  seldom  really  clean,  is  a  very  serious  menace  in 
this  respect.  Under  average  farm  conditions,  unless  a  new  cloth 
strainer  is  used  at  each  milking,  it  is  safe  to  condemn  it  entirely 
and  to  recommend  the  use  of  a  fine  wire  mesh  strainer  containing 
about  eighty  meshes  to  the  inch.  On  some  farms  the  milk  is 
held  in  a  set  of  old  cans  which  are  kept  on  the  farm  and  which 
never  reach  the  can  washer  at  the  factory.  Just  before  hauling 
time  these  cans  are  emptied  into  the  clean  cans  from  the  factory. 
These  old  cans  are  often  not  washed  properly  and  sometimes  not 
at  all.  The  remnants  of  milk  in  these  cans  breed  these  undesir- 
able germs  and  contaminate  the  fresh  milk.  It  is  obvious  that 
such  a  practice  is  bound  to  jeopardize  the  quality  and  life  of  the 
finished  product  and  may  constitute  a  continuous  cause  of  blown 
milk. 

Effect  of  Amount  of  Sucrose. — Since  the  sucrose  contained 
in  sweetened  condensed  milk  is  the  chief  agent  preserving  it, 
it  is  obvious  that  enough  of  it  must  be  added  to  insure  adequate 
preservative  action.  Experience  has  shown  that  about  39  to  40 
per  cent  of  sucrose  is  required  to  preserve  the  condensed  milk 


248  SWSETSNED  CONDENSED  MILK  DEFECTS 

under  average  conditions.  A  higher  per  cent  of  sucrose  would 
naturally  intensify  the  preservative  action  and  inhibit  the  growth 
of  the  bacteria  normally  present  more  completely;  but  if  enough 
sugar  were  added  to  also  inhibit  the  growth  of  and  make  harm- 
less those  violent  gas-producing  butyric  acid  bacteria  and  yeast 
cells,  which  thrive  in  sweetened  condensed  milk  containing  40 
per  cent  sucrose,  the  product  would  be  objectionable  from  the 
consumer's  point  of  view.  The  logical  avoidance  of  "swell 
heads"  as  the  result  of  these  undesirable  germs,  therefore,  must 
ever  lie  in  prevention,  rather  than  cure.  The  sanitary  standard 
of  production  on  the  farm  and  of  the  process  in  the  factory  must 
be  raised  to  and  maintained  on  a  level  where  the  milk  is  pro- 
tected from  contamination  with  these  micro-organisms. 

The  writer1  has  isolated  yeast  from  fermented  sweetened 
condensed  milk  that  produced  vigorous  gas  formation  in  media 
containing  as  high  as  85  per  cent  sucrose  (600  grams  sucrose  in 
100  cc.  whey  bouillon). 

Effect  of  Too  Thin  Condensed  Milk. — Condensed  milk  that 
is  too  thin  is,  also,  prone  to  start  fermenting,  since  it  is  deficient 
in  the  chief  preserving  agents,  i.  e.,  density  and  per  cent  of 
sucrose.  It  is  not  safe  to  put  goods  on  the  market,  with  a  ratio 
of  concentration  much  less  than  2.5  :1,  unless  the  amount  of  cane 
added  is  sufficient  to  raise  the  cane  sugar  content  of  the  fin- 
ished product  to  44  per  cent  or  above. 

Effect  of  Excessively  Low  Temperatures. — The  cans  of 
sweetened  condensed  milk  may  also  bulge  in  the  case  of  cans 
with  non-hermetical  seals,  exposed  successively  to  excessive  cold 
and  to  room  temperature.  In  this  case,  the  condensed  milk  is 
entirely  normal  and  unaffected,  and  the  bulging  is  the  result 
of  mechanical  contraction  and  expansion  by  cold  and  heat.  This 
is  possible  only  where  the  seal  of  the  cans  is  not  entirely  her- 
metical.  In  the  case  of  the  Gebee  seal  with  the  burr  cap,  and 
the  McDonald  seal  with  the  friction  cap,  the  seal  is  not  absolutely 
air-tight.  While  the  pores  betw'een  cap  and  can  are  microscopic 
in  size,  and  not  large  enough  to  permit  the  contents  from  leak- 
ing out,  they  are  sufficient  to  admit  air.  The  cans  are  usually 
filled  with  the  condensed  milk  at  a  temperature  of  about  70  de- 


1  Hunziker,  Results  not  published. 


CONDENSED  MILK  DEFECTS  249 

grees  F.  If  the  filled  and  sealed  cans  are  exposed  to  a  very 
low  temperature,  as  may  be  the  case  in  winter,  in  store  houses  or 
in  transit,  the  milk  and  the  air  in  the  cans  contract.  This  con- 
traction is  intensified  by  the  fact  that  the  sweetened  condensed 
mi'k  does  not  freeze.  Its  concentration  is  so  great  that  its  freez- 
ing point  is  usually  below  the  most  extreme  cold  storage  tem- 
perature. This  contraction  of  milk  and  air  in  the  cans  produces 
a  partial  vacuum,  causing  air  to  be  drawn  into  the  cans  through 
the  microscopic  openings  of  the  seal.  When  the  cans  are  sub- 
sequently moved  into  places  with  a  more  moderate  temperature, 
the  milk  and  the  air  in  the  cans  expand,  but  the  milk  on  the  in- 
side of  the  cans  forms  a  seal  preventing  the  escape  of  the  sur- 
plus air.  The  "result  is  that  the  ends  of  the  cans  bulge.  This, 
phenomenon  has  been  experimentally  determined  by  the  author.1 
While  the  contents  of  such  cans  are  perfectly  normal,  the  pack- 
age suggests  fermented  milk  and  may  be  rejected  on  the  market. 
It  is  evident,  from  the  above  data,  that  the  swelling  of  the 
cans,  as  the  result  of  exposure  to  excessively  low  temperatures, 
can  readily  be  avoided,  either  by  protecting  the  cans  against  ex- 
cessive cold,  or  by  using  cans  that  are  sealed  with  solder.  The 
solder-seals  are  hermetical  so  that  no  air  can  be  drawn  into  the 
cans  when  a  partial  vacuum  is  formed  in  their  interior  as  the 
result  of  the  contraction  of  air  and  milk. 

Rancid  Sweetened  Condensed  Milk. 

General  Description. — Sweetened  condensed  milk  may  de- 
velop a  distinctly  rancid  flavor  and  odor,  a  defect  winch  renders 
it  unmarketable. 

According  to  the  best  authority,  there  are  many  agents 
which  may  be  active  in  the  production  of  rancidity.  The  fact  that 
in  rancid  butter  are  usually  found  to  predominate  certain  species 
of  organisms,  such  as  the  fungi  of  Penicilium  Glaucum,  Penici- 
lium  Roqueforti,  Cladosporium  butyri,  Oidinm  lactis,  Actinomy- 
coces  odorifora,  yeast  and  various  bacterial  species,  such  as  Bac- 
terium fluorescens,  Bacterium  prodigiosum,  Bacillus  mesenteri- 
cus,  etc.,  and  that  these  species  are  capable  of  making  butter  ran- 
cid, has  led  to  the  conclusion  that  they  may  be  the  cause  of  ran- 
cidity, either  by  direct  action,  or  by  the  secretion  of  fat-splitting 

1  Hunziker,  Results  not  published. 


250  SWEETENED  CONDENSED  MILK 

enzymes.  It  is,  therefore,  quite  possible  that  some  of  these  spe- 
cies, or  similar  groups  of  species,  may  be  instrumental  in  develop- 
ing rancidity  in  sweetened  condensed  milk.  It  has  been  further 
found  that  the  milk  products  from  certain  individual  cows,  or 
cows  under  certain  physiological  conditions  are  more  prone  to 
develop  a  rancid  flavor,  than  milk  products  from  other  cows  or 
cows  under  other  conditions. 

Relation  of  Polluted  Water  to  Rancidity. — Polluted  and 
filthy  water  is  usually  contaminated  with  fungi  and  bacteria 
belonging  to  the  species  enumerated  above  and  which  have  been 
found  to  be  able  to  produce  rancidity.  It  is,  therefore,  not  im- 
probable, where  such  water  is  used  in  the  factory  in  the  washing 
of  cans,  conveyors,  kettles,  pipes,  etc.,  in  the  condenser  of  the 
vacuum  pan  and  in  the  cooling  tanks,  as  is  frequently  the  case, 
that  the  contamination  of  milk  with  it  may  result  in  the  develop- 
ment of  rancidity. 

Relation  of  Climate  to  Rancidity. — It  is  frequently  claimed 
that  condensed  whole  milk  shipped  to  the  tropics  turns  rancid, 
owing  to  exposure  of  this  milk,  rich  in  fat  to  a  warm  climate. 
Advantage  is  sometimes  taken  of  this  argument,  to  justify  viola- 
tions of  the  law  by  skimming  all,  or  a  part  of  the  milk  before 
condensing.  This  matter  has  been  thoroughly  investigated.  All 
experimental  results  show  that  sweetened  condensed  milk,  made 
properly  and  in  conformance  with  the  law,  and  containing  all 
the  butter  fat  of  the  original  whole  milk,  does  not  turn  rancid 
at  any  temperature. 

Putrid  Sweetened  Condensed  Milk. 

General  Description. — Sweetened  condensed  milk  is  best 
when  fresh.  With  age  it  gradually  develops  a  stale  flavor  which 
frequently  develops  into  a  putrid  odor  and  flavor. 

Causes  and  Prevention. — The  purer  the  fresh  milk  and  the 
cane  sugar,  and  the  more  careful  the  processor,  the  longer  will 
the  condensed  milk  retain  its  pleasant  flavor,  provided  that  it  is 
stored  at  a  reasonably  low  temperature.  Age,  however,  will 
cause  the  best  sweetened  condensed  milk  to  become  stale.  The 
appearance  of  the  stale  flavor  is  usually  hastened  when  heating 
the  fresh  milk  writh  direct  steam ;  also,  where  the  fresh  milk  is 
not  heated  to  a  sufficiently  high  temperature  (below  176  de- 


SWEETENED  CONDENSED  MILK  DEFECTS  251 

grees  F.)  the  condensed  milk  will  break  down  rapidly  with  age, 
usually  developing  a  putrid  flavor  and  odor.  This  defect  rarely 
appears  where  the  fresh  milk  is  heated  to  180  degrees  F.  or 
above.  This  phenomenon  is  probably  due  to  the  presence  in 
milk  of  active  enzymes,  such  as  galactase,  gradually  decompos- 
ing the  proteids.  The  action  of  most  of  these  enzymes  is 
destroyed  when  the  milk  is  heated  to  176  degrees  F.  or  above. 

Metallic   Sweetened   Condensed  Milk. 

General  Description. — Sweetened  condensed  milk  frequently 
is  pregnant  with  a  very  distinct  metallic  flavor  suggesting  copper. 

Causes  and  Prevention. — This  can  usually  be  traced  back  to 
an  unsanitary  condition  of  the  dome  of  the  vacuum  pan.  The 
sugar  and  acid  in  the  boiling  milk  in  the  pan  tend  to  cause  the 
formation  of  copper  oxide  and  copper  salts,  on  those  sections  of 
the  interior  surface  of  the  pan  which  are  not  daily  completely 
cleansed. 

The  dome  of  the  pan  is  neglected  in  many  condenseries  from 
the  standpoint  of  thorough  cleaning.  If  it  is  permitted  to  go 
uncleansed  for  a  considerable  period  of  time,  it  becomes  coated 
with  copper  salts  and  when  the  pan  is  again  in  operation,  the 
boiling  milk  and  its  spray  \vash  these  metallic  salts  down,  incor- 
porating them  in  the  condensed  milk. 

That  the  copper  in  the  dome  is  being  acted  on  can  be  very 
readily  determined  by  wiping  the  inside  surface  of  the  dome  off 
with  a  wet  sponge,  then  analyzing  the  expressed  liquid  that 
the  sponge  has  absorbed.  This  liquid  will  be  found  to  contain 
varying  amounts  of  copper,  according  to  the  state  of  cleanness 
of  the  dome. 

In  order  to  avoid  metallic  flavor  in  sweetened  condensed 
milk,  the  dome  should  be  washed  down  daily  with  similar  care 
as  is  given  the  cleansing  of  the  jacket,  body  and  coils,  and  each 
morning,  before  the  milk  is  allowed  to  enter  the  pan,  the  entire 
pan,  including  dome  and  gooseneck,  should  be  thoroughly  rinsed 
down  with  plenty  of  clean  water. 

Brown  Sweetened  Condensed  Milk. 

General  Description. — Some  of  the  sweetened  condensed 
milk  on  the  market  has  a  brown  color,  suggesting  chocolate  pud- 
ding. In  this  condition  it  is  usually  rejected  by  the  consumer. 


252  UNSWEETENED  CONDENSED  MILK  DEFECTS 

Causes  and  Prevention. — All  sweetened  condensed  milk  not 
held  at  a  low  temperature  grows  darker  in  color  with  age.  If 
manufactured  properly  and  not  exposed  to  unfavorable  condi- 
tions, this  brown  color  appears  very  gradually  and  not  until  the 
condensed  milk  is  many  months  old.  If  exposed  to  high  tem- 
perature in  storage  or  transportation,  when  stowed  against  the 
boiler  room  in  the  hold  of  the  steamer,  or  lying  on  the  shelves 
of  the  warm  grocery  store  or  drug  store,  etc.,  it  turns  brown 
rapidly.  Condensed  milk  in  cold  storage  retains  its  natural  color 
indefinitely.  Where  milk  is  recondensed  (the  condensed  milk 
is  redissolved  either  in  water  or  in  fresh  milk  and  condensed  a 
second  time),  the  product  is  always  darker  in  color.  This  brown 
color  is  due  to  the  oxidizing  action  of  heat  on  both,  the  lactose 
and  the  sucrose,  a  portion  of  the  sugar  caramelizing.  Experience 
has  shown  that  the  sugar  is  more  sensitive  to'  the  oxidizing 
action  of  the  heat  of  recondensing,  than  when  condensed  the 
first  time. 

CHAPTER    XXIII. 

DEFECTIVE   EVAPORATED    MILK   AND    PLAIN 
CONDENSED    BULK    MILK. 

The  following  are  the  chief  defects  of  unsweetened  condensed 
milk :  curdy,  grainy,  separated  and  churned,  blown  or  fermented, 
brown,  gritty,  metallic. 

Curdy,  Plain  Condensed  Milk  and  Evaporated  Milk. 

General  Description. — Curdy,  unsweetened  condensed  milk 
is  a  term  used  for  milk  in  which  a  part  of  the  casein  is  precip- 
itated in  the  form  of  lumps  of  various  sizes.  The  appearance 
of  lumps  of  curd  in  this  product  is  a  defect  that  may  render  the 
goods  unsalable. 

Causes  and  Prevention. — -Lumps  are  usually  due  to  a  poor 
quality  of  fresh  milk,  the  use  of  excessive  heat  in  the  sterilizing 
process  and  too  high  a  degree  of  concentration. 

Lumps  in  Plain  Condensed  Bulk  Milk. — Lumps  are  prone 
to  appear  in  plain  condensed  bulk  milk,  as  this  class  of  goods  is 
usually  made  from  fresh  milk  that  may  be  slightly  sour,  as  is  the 
case  in  creameries  and  in  milk  plants  where  the  surplus  and  the 


UNSWEETENED  CONDENSED  MILK  DEFECTS  253 

returned  milk  is  often  manufactured  into  plain  condensed  bulk 
milk.  This  defect  can  be  avoided  by  neutralizing  the  milk  before 
heating,  with  an  alkali  (sodium  bicarbonate  or  lime  water),  heat- 
ing less  intensely,  or  by  not  carrying  the  condensing  process  quite 
so  far.  If  the  plain  condensed  bulk  milk  comes  from  the  pan  in 
lumpy  condition,  it  can  usually  be  reduced  to  a  smooth  body  by 
passing  it  through  an  ice  cream  freezer  at  ordinary  temperatures. 

Lumps  of  Curd  in  Evaporated  Milk. — The  danger  of  lump- 
iness,  or  curdiness  in  evaporated  milk  is  greatly  augmented  by 
the  fact  that,  in  addition  to  the  causes  named  under  plain  con- 
densed bulk  milk,  the  sterilizing  process  must  be  dealt  with. 
The  high  sterilizing  temperature  used,  tends  to  precipitate  the 
proteids  of  milk,  and  the  temperature  cannot  be  reduced  below 
certain  limits  without  impairing  the  keeping  quality  of  the  pro- 
duct. Most  of  the  evaporated  milk,  after  sterilization,  is  sub- 
jected to  the  shaking  process  in  which  the  coagulum  in  the  cans 
is  reduced  to  a  homogeneous  creamy  fluid,  provided  that  the  curd 
is  not  too  hard.  A  curd  will  form  in  the  sterilizer  in  the  majority 
of  cas£S.  If  it  is  soft  enough,  so  that  it  can  be  completely  broken 
up,  no  harm  is  done.  If  it  is  so  firm  that  mechanical  shaking 
fails  to  cause  it  to  disappear,  then  the  evaporated  milk  will  reach 
the  market  in  lumpy  condition  and  is  difficult  to  sell. 

Effect  of  Quality  of  Fresh  Milk.— The  quality  of  fresh  milk 
is  all  important  in  preventing  lumpy  evaporated  milk.  The  milk 
must  come  from  healthy  cows  in  good,  normal  physical  condition. 
It  must  not  contain  colostrum  milk  nor  be  stripper  milk  and  it 
must  receive  the  best  of  care  on  the  farm  and  reach  the  factory 
perfectly  sweet.  Milk  that  is  not  of  high  quality  in  every  respect 
should  not  be  received  at  the  factory. 

The  acidity  of  milk  due  to  acid  fermentation,  lowers  the 
curdling  point  of  the  milk,  partly  by  changing  the  reaction  and 
partly  by  lowering  the  citric  acid  content.  High  acidity  there- 
fore is  one  of  the  causes  of  curd  formation  in  evaporated  milk. 
If  abnormal  curdling  is  to  be  prevented,  one  of  the  first  and  fun- 
damental essentials  is  that  the  milk  reach  the  condensery  in  as 
fresh  and  sv/eet  a  condition  as  possible. 

Effect  of  Relation  of  Mineral  Constituents  of  Milk. — More 
recent  studies  of  the  heat  coagulation  of  milk,  however,  by  Som- 


254  UNSWEETENED  CONDENSED  MILK  DEFECTS 

mer  and  Hart,1  and  by  Rogers2  show  that  the  titratable  acidity 
of  fresh  milk  is  not  the  only,  and  often  not  the  really  important 
factor,  controlling  the  coagulation  of  milk,  but  that  the  stability 
of  the  casein,  or  its  resistance  to  the  coagulating  effect  of  ex- 
posure to  heat,  depends  on  the  relation  of  certain  ash  constit- 
uents. 

Sommer  and  Hart  conclude  that  maximum  stability  of  the 
casein  demands  a  proper  balance  of  calcium  and  magnesium  with 
the  phosphates  and  citrates,  while  the  sodium  and  potassium 
chlorides  in  the  concentrations  present  do  not  have  any  marked 
influence  on  the  coagulating  point.  Thus  these- investigators  state, 
the  coagulation  of  milk  on  heating  may  be  due  either  to  an  excess 
or  a  deficiency  of  calcium  and  magnesium.  The  calcium  in  the 
milk  distributes  itself  between  the  casein,  citrates,  and  phos- 
phates chiefly.  "If  the  milk  is  high  in  citrate  and  phosphate 
contents,  more  calcium  is  necessary  in  order  that  the  casein 
may  retain  its  optimum  calcium  content  after  competing  with 
the  citrates  and  phosphates.  If  the  milk  is  high  in  calcium, 
there  may  not  be  sufficient  citrate  and  phosphate  to  compete 
with  the  casein  to  lower  its  calcium  content  to  the  optimum. 
In  such  a  case  the  addition  of  citrates  or  phosphates  makes  the 
casein  more  stable  by  reducing  its  calcium  content.  The  magne- 
sium functions  by  replacing  the  calcium  in  the  citrates  and 
phosphates. 

"In  most  cases  the  coagulation  is  due  to  an  excess  of  calcium 
and  magnesium.  It  is  possible  to  balance  this  excess  by  citrates, 
phosphates,  carbonates  and  other  salts."  See  also  Chapter  XI 
on  "Sterilizing,"  Mojonnier  Viscosity  Controller. 

The  factors  of  relation  of  ash  constituents  are  influenced 
and  largely  controlled  by  such  conditions  as  breed,  period  of 
lactation,  health  and  feed  of  the  cows.  And  this  fact  in  turn 
may  be  accepted  to  explain,  why  there  is  a  vast  difference  in 
the  ability  of  milk  produced  in  different  localities,  to  withstand 
different  degrees  of  concentration  and  sterilization  without 
developing  a  permanent  and  objectionable  curd.  It  is  a  well 


1  H.   H.    Sommer   and  E.    B.   Hart,   The   Heat  Coagulation   of   Milk,    Jour. 
Biol.   Chemistry,  Vol.  XL,  No.    1,   1919. 

2 1*.    A.    Rogers,    Address,    Milk    Section    National    Canners'    Association, 
Cleveland,   O.,    1920. 


UNSWEETENED  CONDENSED  MILK  DEFECTS  255 

known  fact,  established  by  practical  experience  in  processing, 
and  by  analyses  of  different  brands  of  evaporated  milk,  that  in 
some  European  countries,  milk  can  be  condensed  to  a  much 
higher  degree  of  concentration  than  in  most  sections  of  this 
country,  without  becoming  permanently  curdy. 

Effect  of  Forewarming  or  Preheating  on  Curdling. — As  ex- 
plained in  Chapter  XI  on  "Sterilizing/*  under  "Factors  that 
Decrease  Viscosity  of  Evaporated  Milk,"  the  readiness  with 
which  milk  coagulates  in  the  sterilizer  is  diminished  by  lengthen- 
ing the  period  of  preheating  in  the  forewarmer,  or  by  raising  the 
temperature  of  preheating,  or  both.  And  vice  versa,  the  shorter 
the  period  of  preheating  and  the  lower  the  temperature  (below 
210  degrees  F.)  to  which  the  milk  is  foreWarmed,  other  conditions 
being  the  same,  the  greater  the  danger  of  curdling  in  the  steril- 
izer. 

It  is  not  improbable  that  here  again  the  modification  of  the 
balance  of  the  calcium  and  magnesium  with  the  phosphates  and 
citrates,  may  be  the  fundamental  cause  of  these  phenomena. 
In  this  case  the  longer  exposure  to  the  forewarming  heat,  or  the 
higher  temperature  of  forewarming,  or  both,  may  have  the  effect 
of  lowering  the  soluble  calcium  content  by  precipitating  part  of 
it  as  insoluble  calcium  phosphate.  If  coagulation  is  due  to  an 
excess  of  calcium  or  magnesium,  as  it  usually  is,  then  this  lower- 
ing of  the  calcium  content,  as  the  result  of  preheating,  will  mini* 
mize  the  danger  of  coagulation  in  the  sterilizer. 

Effect  of  Addition  of  Water  on  Curdling. — Addition  of  ex- 
traneous water  to  the  evaporated  milk  lessens  the  intensity  of 
coagulation  in  the  sterilizer.  This  is  a  matter  pretty  generally 
understood  by  the  experienced  operator,  as  pointed  out  in  Chapter 
XI  on  "Sterilizing"  under  "Factors  which- Decrease  Viscosity 
and  Tendency  to  Curdle."  It  is  due  to  the  dilution  of  both  the 
casein  and  the  serum  in  milk. 

Effect  of  Concentration. — The  more  concentrated  the  evap- 
orated milk,  the  greater  the  danger  of  lumpiness.  All  the  con- 
ditions causing  lumpiness  are  intensified  by  the  degree  of  con- 
centration.1 The  manufacturer  must,  therefore,  study  the  be- 

1  For  detailed  discussion  of  relation  of  quality  of  fresh  milk  to  curdinese 
of  evaporated  milk  see  Chapter  VIII  on  "Manufacture  of  Evaporated  Milk," 
"Quality  of  Fresh  Milk." 


256  UNSWEETENED  CONDENSED  Miut  DEFECTS 

havior  of  his  product  at  different  degrees  of  concentration,  and 
then  decide  how  much  evaporation  it  will  staad  without  develop- 
ing subsequently  a  permanent  curd  in  the  sterilizer.1 

It  is  obvious  that  any  excess  or  deficiency  of  calcium,  or 
any  excess  of  acid  present  in  the  original  milk,  is  magnified  in 
direct  proportion  as  the  concentration  increases.  Therefore,  the 
higher  the  concentration,  the  more  difficult  it  is  to  put  the  evap- 
orated milk  through  the  sterilizing  process  without  the  formation 
of  a  permanent  curd. 

Effect  of  Sterilization. — The  coagulum  is  formed  in  the 
sterilizer.  The  higher  the  temperature,  other  conditions  being 
the  same,  the  firmer  the  curd.  The  lowest  temperature  that  will 
efficiently  sterilize  the  evaporated  milk  should,  therefore,  be 
used.  Since  the  sterilizing  temperature  to  be  maintained  cannot 
be  modified  below  certain  limits,  it  is  necessary,  when  the  milk 
is  very  sensitive  to  the  heat,  to  lower  the  degree  of  concentration. 
In  some  factories  fractional  sterilization  is  resorted  to  with 
batches  of  milk  that  are  suspicious.  By  so  doing,  lower  tem- 
peratures can  be  used  effectively,  but  this  process  calls  for  much 
more  labor,  increases  the  cost  of  manufacture  and  decreases  the 
capacity  of  the  factory. 

Effect  of  Fractional  Curdling. — Experience  has  shown  that, 
if  the  proteids  in  evaporated  milk  are  partly  precipitated  by  heat 
before  the  milk  reaches  the  sterilizer,  the  curd  or  lumps  formed 
in  the  sterilizer  are  less  firm  and  can  be  shaken  out  more  readily. 
It  is,  therefore,  advisable  to  heat  the  milk  in  the  forew.armers  to 
as  near  the  boiling  point  as  possible  and  to  hold  it  at  that  tem- 
perature for  at  least  five  minutes  before  it  is  drawn  into  the  pan. 
The  superheating  of  the  evaporated  milk  before  it  leaves  the  pan 
is  an  additional  safeguard  against  the  formation  of  excessive  curd 
in  the  sterilizer. 

Effect  of  Homogenizing  Evaporated  Milk.— Excessive  pres- 
sure in  the  homogenizer  tends  to  so  change  the  physical  prop- 
erties of  the  casein  as  to  render  it  more  sensitive  to  the  steriliz- 
ing process.  Evaporated  milk,  homogenized  under  excessive 
pressure  almost  invariably  forms  a  firm,  unshakable  curd  in  the 

1  For  detailed  discussion  see  Chapter  VIII,  on  "Striking,"  and  Chapter  XI, 
on  "Sterilizing." 


CONDENSED  Miuc  DEFECTS  257 

sterilizer.  The  homogenizing  pressure  should  be  kept  down  to 
one  thousand  to  fifteen  hundred  pounds.1 

Effect  of  Addition  of  Bicarbonate  of  Soda. — As  shown  in 
Chapter  XI  on  "Sterilizing"  the  addition  to  the  evaporated  "milk 
of  bicarbonate  of  soda  diminishes  the  viscosity  and  tendency  to 
curdle  in  most  cases. 

This  is  due  to  the  fact,  that  in  most  cases,  the  coagulation 
is  due  to  an  excess  of  calcium  and  magnesium,  which  lowers  the 
stability  of  the  casein.  The  addition  of  carbonates  in  the  form 
of  bicarbonate  of  soda  reduces  the  excess  of  calcium  and  mag- 
nesium, assists  in  balancing  these  mineral  constituents,  and 
thereby  makes  the  casein  more  stable. 

Occasionally  it  happens,  however,  that  the  addition  of  sodi- 
um bicarbonate  increases,  instead  of  decreases,  the  viscosity  and 
coagulability  of  the  evaporated  milk,  and  in  such  cases,  the  diffi- 
culty increases  in  direct  proportion  with  the  amount  of  bicarbon- 
ate added.  In  this  case  the  viscosity  and  coagulability  of  the 
evaporated  milk  are  undoubtedly  due,  not  to  an  excess  of  calcium 
as  is  usually  the  case,  but  to  a  deficiency  of  calcium.  Under  such 
conditions  a  soluble  calcium  or  magnesium  salt  should  be  added 
in  the  place  of  bicarbonate,  in  order  to  diminish  the  viscosity 
and  to  render  the  casein  more  stable. 

Acid  Flux  in  the  Cans  Causes  Lumps. — Similar  as  in  the  case 
of  the  sweetened  condensed  milk,  the  presence  of  acid  flux  in  the 
cans  of  evaporated  milk  causes  lumpiness.  The  acid  that  reaches 
the  interior  of  the  cans  causes  the  milk  coming  in  contact  with 
the  seams  to  curdle.  Only  acid-free  flux  should  be  used  in  the 
manufacture  and  sealing  of  the  cans. 

Grainy  Evaporated  Milk. 

General  Description. — This  term  is  sometimes  applied  to 
lumpy  milk,  in  which  case  it  means  the  same.  By  grainy  milk, 
however,  is  generally  understood  milk  which  contains  a  sediment 
of  a  white  granular  appearance,  which  is  insoluble. 

Causes  and  Prevention. — This  granular  sediment  is  largely 
found  in  the  hermetically  sealed  cans  after  the  sterilizing  process. 
It  is  due  to  excessively  high  sterilizing  temperatures  or  too  long 

1  For  detailed  discussion  of  the  effect  of  homogenizing  on  curdiness  see 
Chapter  IX  on  "Homogenizing'"  and  Chapter  XXIII  on  "Separated  and  Churned 
Evaporated  Milk." 


258  UNSWEETENED  CONDENSED  MILK  DEFECTS 

exposure  of  the  milk  to  the  process.  It  consists  largely  of  the 
mineral  matter  of  milk,  rendered  insoluble  and  precipitated  by 
heat.  The  use  of  lower  sterilizing  temperatures  or  the  shorten- 
ing of  the  period  of  sterilization  will  help  to  avoid  this  defect. 

Evaporated  milk  in  the  condensation  of  which  the  "Continu- 
ous Concentrator"  was  used,  has  a  tendency  to  show  slight  grainy 
condition,  though  this  is  barely  perceptible. 

Separated  and  Churned  Evaporated  Milk. 

General  Description. — This  is  a  very  common  defect.  A 
portion  of  the  butter  fat  of  the  contents  of  the  hermetically 
sealed  cans,  has  separated  and  appears  in  the  form  of  lumps  of 
cream  or  of  churned  butter,  on  top  of  the  evaporated  milk.  While 
this  separated  evaporated  milk  is  normal  in  quality  and  whole- 
someness,  its  appearance  condemns  it. 

Causes  and  Prevention. — As  explained  in  Chapter  IX  on 
"Homogenizing,"  the  fundamental  cause  of  separated  and 
churned  evaporated  milk  lies  in  the  difference  of  the  specific 
gravity  between  the  butter  fat  and  the  rest  of  the  milk  constitu- 
ents. The  fat  globules,  being  lighter  than  the  serum,  tend  to 
rise  to  the  surface,  forming  a  layer  of  thick  cream.  When  this 
separated  evaporated  milk  is  subjected  to  agitation,  as  is  the 
case  in  transportation,  this  cream  churns  into  lumps  of  butter. 
This  tendency  of  the  fat  to  separate  in  storage  and  churn  in 
transportation,  increases  with  the  increase  of  the  size  of  the  fat 
globules,  because  the  larger  the  globules,  the  larger  is  their  cubic 
content  in  proportion  to  their  surface.  This  fact  is  based  on  the 
well  known  physical  law,  that  the  surfaces  of  two  spheres  are 
to  each  other  as  the  squares  of  their  diameters,  and  the  cubic 
contents  of  two  spheres  are  to  each  other  as  the  cubes  of  their 
diameters.  The  cubic  contents  determine  the  gravity  force,  or 
buoyancy,  while  the  surfaces  control  the  resistance  force.  There- 
fore, the  larger  the  fat  globules  the  greater  is  their  buoyancy 
and  the  weaker  is  the  relative  resistance  which  they  must  over- 
come in  their  upward  passage. 

Effect  of  Locality  and  Season. — Since  the  predominating 
size  of  fat  globules  in  milk,  varies  with  breed  and  period  of 
lactation  of  the  cows,  the  ease  with  which  evaporated  milk 


UNSWEETENED  CONDENSED  MILK  DEFECTS  259 

separates  and  the  difficulty  of  overcoming  this  defect,  differ 
greatly  with  locality  and  season  of  year.  The  fat  globules  in 
milk  from  the  Channel  Island  breeds,  average  two  to  three  times 
as  large  as  those  in  milk  from  the  Holsteins  and  Ayrshires. 
Therefore,  factories,  located  in  Holstein  and  Ayrshire  territories 
are  not  troubled  nearly  as  much  with  fat  separation  in  evap- 
orated milk,  as  factories  in  localities  where  Jerseys  and  Guernseys 
predominate. 

Again,  the  fat  globules  are  largest  at  the  beginning  of  the 
period  of  lactation  and  decrease  in  size  as  the  period  of  lactation 
advances. 

In  order  to  equalize  the  output  of  evaporated  milk  through- 
out the  year,  condensing  concerns  make  every  effort  to  induce 
their  patrons  to  time  the  breeding  of  their  cowts  in  such  a  way 
that  the  fresh  cows  are  distributed  throughout  the  year.  The 
result  of  this  practice  is,  that  the  milk  supply  of  these  factories 
represents  at  all  times  a  mixture  of  milk  from  cows  at  all  stages 
of  their  period  of  lactation.  This  naturally  equalizes  the  be- 
havior of  the  finished  product  as  far  as  separation  of  the  fat  is 
concerned,  facilitating  the  control  of  this  separation.  On  the 
other  hand,  in  localities  of  factories,  newly  established,  summer 
milk  is  largely  produced  and  the  majority  of  cows  freshen  in  the 
spring.  This  causes  a  marked  increase  of  the  size  of  the  average 
fat  globules  in  early  summer,  rendering  the  manufacture  of 
evaporated  milk,  that  does  not  separate  its  fat,  more  difficult. 

Effect  of  Degree  of  Concentration. —  Other  conditions  being 
the  same,  the  more  concentrated  the  product,  the  less  the  danger 
of  fat  separation  in  the  finished  product.  The  leason  for  this 
lies  in  the  fact  that  with  the  concentration  the  viscosity  and  the 
resistance  force  of  the  evaporated  milk  increase,  hindering  the 
fat  globules  in  their  upward  passage.  This  is  partly  offset  by 
the  increase  in  the  specific  gravity  of  the  product,  but  the  in- 
crease of  the  resistance  force  exerts  a  stronger  influence  against 
separation  of  the  fat,  than  the  increase  of  the  gravity  force  exerts 
in  favor  of  fat  separation. 

However,  as  the  concentration  increases,  the  evaporated 
milk  becomes  more  sensitive  to  the  sterilizing  process  aaid 
beyond  certain  limits  it  would  be  necessary  to  reduce  the  tem- 
perature or  the  length  of  exposure  to  heat,  or  both,  in  order  to 


260  UNSWEETENED  CONDENSED  MILK  DEFECTS 

prevent  the  more  highly  concentrated  milk  from  becoming  per- 
manently curdy.  If,  in  order  to  increase  the  viscosity,  the  degree 
of  concentration  is  carried  so  far  that  the  sterilizing  process  has 
to  be  shortened,  nothing  is  gained  but  much  may  be  lost.  It 
is  obvious,  therefore,  that  the  degree  of  concentration  does  not 
furnish  a  practical  basis  for  controlling  fat  separation. 

Effect  of  the  Sterilizing  Process. — Prolonged  exposure  of 
the  evaporated  milk  to  the  sterilizing  heat  tends  to  so  change  the 
physical  properties  of  the  albuminoids,  as  to  render  the  product 
more  viscous.  Within  the  limits  of  the  necessary  sterilizing  heat, 
long  exposure  to  moderate  heat  is  more  effective  in  this  respect 
than  short  exposure  to  a  high  degree  of  heat.  Since  the  greater 
viscosity  tends  to  keep  the  fat  globules  from  rising,  the  use  of 
a  prolonged  sterilizing  process,  in  which  the  heat  is  applied 
slowly,  is  more  effective  in  preventing  fat  separation  in  the 
evaporated  milk  than  a  rapid,  short  process,  in  which  the  tem- 
perature used  is  very  high. 

It  should  be  understood  from  the  discussion  in  previous 
chapters  that,  in  regulating  the  process  of  sterilization,  the  pro- 
cessor should  be  governed  by  the  condition  and  behavior  of  the 
milk  and  that  on  the  one  hand  the  degree  and  duration  of  heat 
should  always  be  sufficient  to  insure  absolute  sterility  of  the 
product,  while  on  the  other  he  must  guard  against  the  formation 
of  an  unshakable  curd.1 

Effect  of  Superheating. — The  superheating  of  the  milk  be- 
fore sterilization  and  the  stopping  of  the  reel  of  the  sterilizer 
as  explained  under  "Sterilization,"  also  tend  to  so  jncrease 
the  viscosity  of  the  evaporated  milk  as  to  minimize  its  tendency 
to  separate  its  fat.  But  here  again  good  judgment  is  required, 
otherwise  there  is  danger  of  spontaneous  thickening  of  the  prod- 
uct after  manufacture. 

Turning  the  Cans  in  Storage. — Many  manufacturers,  in  an 
effort  to  avoid  fat  separation,  have  adopted  the  practice  of  turn- 
ing their  goods  in  storage  at  regular  intervals.  This  operation 
naturally  interferes  with  and  retards  the  rising  of  the  fat  to  the 
surface,  as  long  as  the  goods  remain  in  the  factory.  After  they 
leave  the  factory  this  control  must  of  necessity  cease  and  if  the 


1  For  detailed  discussion  see  Chapter  XI  on  "Sterilizing." 


UNSWEETENED  CONDENSED  MILK  DEFECTS  261 

evaporated  milk,  owing  to  the  process  of  manufacture  and  the 
condition  of  the  product,  is  destined  to  separate  its  fat,  the  turn- 
ing of  the  cases,  while  at  the  factory,  cannot  permanently  prevent 
separation.  Where  the  goods  are  consumed  immediately  after 
they  leave  the  factory, "this  practice  may  serve  the  purpose;  but, 
since  the  large  bulk  of  evaporated  milk  manufactured,  is  exposed 
to  prolonged  storage,  its  advantage  is  very  limited. 

Effect  of  Homogenizing. — Under  average  conditions  careful 
attention  to  the  precautions  above  discussed  will  greatly  mini- 
mize and  often  prevent  fat  separation.  At  best,  however,  much 
of  the  evaporated  milk  on  the  market  shows  signs  of  separation 
after  sixty  to  ninety  days  and  some  of  it  even  after  two  weeks, 
for  the  fundamental  cause  of  separation,  the  difference  in  gravity 
between  the  fat  globules  and  the  rest  of  the  milk  constituents, 
is  still  present;  then  again,  under  less  favorable  conditions,  even 
the  above  precautions  may  not  prove  adequate  to  keep  the  fat 
from  separating. 

The  introduction  of  any  agent  or  process,  therefore,  capable 
of  permanently  removing  this  fundamental  cause,  must  prove 
a  lasting  benefit  to  the  manufacturer  of  evaporated  milk.  This 
agent  has  been  found  in  the  homogenizer.  The  homogenizer 
makes  it  possible  to  divide  the  fat  globules  so  finely,  that  their 
buoyancy  or  gravity  force  is  not  great  enough  to  overcome  the 
resistance  of  the  surrounding  liquid.  They  are  unable  to  rise  to 
the  surface,  but  remain  in  homogeneous  emulsion. 

It  is  quite  probable  that  aside  from  the  reduction  of  the  size 
of  the  fat  globules,  the  efficiency  of  the  homogenizer  to  prevent 
fat  separation  is  due  also  to  the  physical  change  of  the  casein  as 
the  result  of  homogenization.  The  casein  becomes  more  viscous. 

The  chief  objection  to  the  use  of  the  homogenizer  is  its 
effect  on  the  casein  of  the  milk,  when  subjected  to  excessive  pres- 
sure. Beyond  certain  limits  of  pressure  homogenization  so 
affects  the  casein,  that  the  latter  is  more  prone  to  curdle  in  the 
sterilizer.  However,  experience  has  amply  shown  that  the  maxi- 
mum pressure  required  to  prevent  fat  separation  in  the  finished 
product,  is  not  great  enough  to  seriously  affect  the  behavior  of 
the  casein  during  sterilization.  Hence,  the  proper  regulation  of 


262  UNSWEETENED  CONDENSED  MILK 

the  pressure  and  the  intelligent  use  of  the  homogenizer,  furnish 
a  satisfactory  and  reliable  means  to  prevent  fat  separation.1 

Fermented  Evaporated  Milk. 

Genera!  Description. — Fermented  evaporated  milk  is  evap- 
orated milk,  which  after  sterilization,  has  undergone  fermenta- 
tion". The  type  of  fermentations  found  in  this  product  varies 
with  locality,  season  of  year  and  factory  conditions.  The  con- 
tents of  the  cans  may  have  soured  with  curd  formation,  or  a 
curd  may  have  formed  without  acid  development,  or  the  fer- 
mentation may  be  gaseous,  in  which  case  the  cans  bulge,  and 
these  gaseous  fermentations  may  be  accompanied  by  acid  "forma- 
tion or  by  putrefactive  products.  In  all  cases  of  fermented  milk 
the  product  is  entirely  worthless.  These  defects  are  usually, 
though  not  always,  detected  during  the  period  of  incubation. 

Fermented  evaporated  milk  is  the  result,  either  of  incomplete 
sterilization,  or  of  leaky  cans.  The  causes  of  fermented  evap- 
orated milk  differ  with  the  specific  type  of  fermentations  pro- 
duced ;  they  will  be  discussed  separately  and  as  relating  to  the 
respective  types  of  fermentations. 

Acid  Fermentation,  Sour,  Curdled,  Evaporated  Milk. 

General  Description. — Upon  opening  the  cans  the  contents 
are  found  to  be  sour  and  curdy. 

Causes  and  Prevention. — This  condition  is  the  result  of  the 
presence  of  acid-producing  species  of  micro-organisms,  usually 
of  the  lactic  acid  type,  which  sour  the  milk,  and  the  acid  produced 
curdles  the  casein.  Since  the  majority  of  the  lactic  acid  bacteria 
are  not  resistant  to  heat  and  are  destroyed  at  relatively  low  heat, 
this  defect  is  not  usually  caused  by  incomplete  sterilization.  The 
temperature  of  sterilization,  though  it  might  be  insufficient  to 
kill  spore  forms,  is  high  enough  to  make  it  impossible  for  lactic 
acid  bacteria  to  pass  the  process  alive. 

The  only  way  in  which  this  defect  can  occur  is  through  sub- 
sequent contamination  of  the  contents  of  the  cans  with  these 
germs,  and  the  only  possible  channel,  through  which  this  sub- 
sequent contamination  may  occur,  is  leaky  cans,  or  leaky  seals. 

1  For  details  on  the  use  of  homogenizer  see  Chapter  IX  on  "Homogeniz- 
ing." 


UNSWEETENED  CONDENSED  MILK  DEFECTS  263 

A  careful  examination  of  the  cans  of  sour,  curdled  evaporated 
milk  usually  shows  faulty  cans  or  faulty  seals. 

Bitter  Curd. 

General  Description. — When  the  cans  are  opened  the  con- 
tents present  a  solid  coagulum,  generally  noticeably  white  in 
color  and  very  bitter  to  the  taste,  similar  to  the  bitterness  of 
dandelions.  There  is  a  separation  of  practically  clear  whey,  the 
curd  does  not  break  down  readily  upon  shaking  and  the  acid 
reaction  of  the  mixture  of  curd  and  whey  is  about  .35  to  .40  per 
cent,  which  is  normal  for  evaporated  milk. 

Causes  and  Prevention. — Microscopic  examinations  under 
high  magnification  of  cultures  in  sterile  milk  show  the  presence 
of  very  small  bacilli.  The  milk  forms  a  firm  coagulum  in  five  to 
seven  days  and  when  over  one  week  old  the  curd  has  the  same 
strong,  bitter  taste  as  that  in  the  cans.  The  bitterness  increases 
with  age.  These  bacilli  grow  best  at  90  degrees  F.  They  are 
facultative  anaerobes,  developing  both,  in  aerobic  and  anaerobic 
media,  but  prefer  anaerobic  conditions. 

In  the  cases  under  observation  no  spores  were  detected  and 
exposure  for  fifteen  minutes  to  212  degrees  F.  destroyed  these 
germs.  The  above  findings  do  not  exclude  the  possibility  of  spore 
formation  under  conditions  very  unfavorable  to  growth  and  life. 

The  presence  of  this  species  of  bitter  curd  organisms  sug- 
gests incomplete  sterilization  of  the  evaporated  milk.  The  strik- 
ing whiteness  of  the  curd  in  all  cases  that  have  come  to  the 
writer's  attention,  is  further  proof  of  the  correctness  of  this  de- 
duction. It  indicates  that  these  cans  received  relatively  little 
heat  in  the  sterilizer,  otherwise  the  curd  would  have  a  darker 
color.  This  defect  usually  does  not  show  up  in  all  the  cans  of 
one  and  the  same  batch,  but  only  in  a  limited  portion  of  each 
batch.  This  fact  suggests  that  the  distribution  of  heat  in  the 
sterilizer  is  not  uniform,  some  cans  getting  less  heat  than  others. 

This  defect  occurs  generally  in  summer,  a  fact  which  may  be 
due  to  one  or  both  of  the  following  conditions : 

While  it  is  well  known  that  there-  is  a  group  of  species  of 
bacteria,  yeast  and  torula  that  are  capable  of  producing  a  bitter 
curd,  either  direct,  or  through  the  secretion  of  casein-curdling 


264  UNSWEETENED  CONDENSED  MILK  DEFECTS 

enzymes,  and  while  these  different  species  of  micro-organisms 
come  from  a  variety  of  sources,  the  most  common  sources  are, 
the  soil,  pasture,  water  and  the  udder  itself.  It  is  a  noteworthy 
fact  that  this  defect  is  most  commonly  found  in  milk  and  milk 
products  when  the  cows  are  on  pasture.  It  is,  therefore,  probable 
that,  in  most  cases,  this  troublesome  germ  is  carried  into  the  milk 
on  the  farm. 

Again,  in  summer,  at  a  time  when  this  defect  generally 
occurs,  the  effect  on  the  cows  of  the  summer  heat  and  flies,  and 
the  tendency  toward  high  acid  in  milk,  render  the  milk  most 
sensitive  to  the  sterilizing  heat.  The  operator  finds  it  difficult 
to  avoid  the.  formation  of  a  disastrous  curd  in  the  sterilizer.  In 
order  to  guard  against  this  trouble  he  is  tempted  to  either  lower 
the  temperature,  or  shorten  the  duration  of  the  sterilizing  process. 
This  tends  towards  incomplete  sterilization.  .  A  very  frequent 
result  of  this  "  incomplete  sterilization  in  the  late  summer 
months,  is  the  formation  of  a  bitter  curd.  When  the  processor 
returns  to  the  proper  sterilizing  process,  the  occurrence  of  bitter 
curd  in  the  cans  disappears  and  the  product  is  normal. 

A  further  safeguard  against  the  recurrence  of  this  trouble 
lies  in  providing  for  uniform  distribution  of  heat  in  the  sterilizer. 
If  the  cans  have  to  be  stacked  in  deep  tiers,  which  is  un- 
desirable and  should  be  avoided,  slats  should  be  placed  over 
the  top  of  every  second  row  of  cans.  This  will  make  possible 
the  free  access  of  steam  to  at  least  one  end  of  each  can.  If  the 
circulation  of  steam  in  the  sterilizer  is  poor,  the  uniform  distribu- 
tion of  heat  can  be  facilitated  by  filling  the  sterilizer  about  one- 
third  full  of  water  so  that,  with  every  revolution  of  the  frame- 
work, the  cans  have  to  pass  through  this  water  once.  The  water 
reaches  every  nook  in  the  interior  of  the  sterilizer,  distributing 
the  heat  much  more  uniformly  than  the  steam.  Uneven  distribu- 
tion of  the  heat  may  also  be  due  to  an  improper  condition  of  the 
steam-distributing  pipe  located  in  the  bottom  of  the  sterilizer. 
Some  of  the  perforations  in  this  pipe  may  have  become  too  large 
by  wear,  or  may  have  become  clogged  with  scale  or  the  cap 
at  the  end  of  the  pipe  may  have  come  off.  In  all  of  these  cases 
the  distribution  of  the  heat  in  the  sterilizer  is  found  to  be  irregular, 
interfering  with  the  uniformity  and  dependability  of  the  proces's 
of  sterilization.  The  processer  should  make  sure,  by  daily  in- 


UNSWEETENED  CONDENSED  MILK  DEFECTS  265 

spection,  that  the  steam-distributing  pipe  is  in  proper  operating 
condition.  If  these  precautions  fail  to  remedy  the  trouble,  then 
the  entire  process  is  inadequate  and  either  more  heat,  or  longer 
exposure  to  the  same  heat  is  necessary. 

Spitzer  and  Epple1  investigated  a  case  of  bitter  evaporated 
milk,  in  which  the  troublesome  organism  appears  to. have  been 
of  a  different  type  than  was  the  case  in  the  bitter  evaporated 
milk  epidemics  under  observation  by  Hunziker,  as  described 
above.  Spitzer  and  Epple  found  the  bitterness  to  be  due  to  the 
presence  in  the  evaporated  milk,  of  an  organism  that  corresponds 
with  Migula's  (1900)  classification  of  Bacillus  panis  as  described 
by  Lawrence  and  Laubach.2 

This  organism  is  a  non-motile  bacterium,  rod-shape,  with 
rounded  ends  and  measuring  about  .4  by  2.0  microns.  It  is  spore- 
bearing,  the  spores  forming  readily  in  48  to  72  hours  and  ap- 
pearing usually  near  the  center  of  the  rod.  The  organism  is 
capsulated  and  is  very  resistant  to  heat.  Spitzer  and  Epple 
found  it  to  survive  a  temperature  of  250  degrees  F.  for  8  minutes, 
but  was  destroyed  at  the  same  temperature  upon  10  minute 
exposure.  The  organism  does  not  form  gas,  it  does  not  swell 
the  cans,  nor  does  it  coagulate  the  casein.  The  contents  of  the 
cans  appear  perfectly  normal  to  the  eye,  the  only  change  noticeable 
is  the  intensely  bitter  taste.  It  is  an  active  proteolytic  germ 
capable  of  secreting  enzymes  which  are  proteolytically  active, 
rapidly  breaking  down  the  proteids  of  milk  into  large  quantities 
of  peptones  and  lower  nitrogenous  compounds  of  complex  nature. 
The  authors  suggest  that  the  excessive  peptonizing  function  of 
this  organism  may  be  the  primary  cause  of  the  bitterness. 

The  description  of  the  cultural  characteristics  and  thermal 
death-point  of  this  organism  suggests  that  the  presence  of  this 
germ  in  the  evaporated  milk,  and  the  spoilage  of  the  product, 
are  not  due  to  a  faulty  process  of  sterilization,  but  are  the  result 
of  conditions  in  the  factory  that  permit  this  germ  to  lodge  and 
to  contaminate  the  milk.  Unsanitary  condition  of  pipes,  pumps, 
homogenizer,  filling  machine,  etc.,  would  be  the  most  likely 
breeding  places  and  sources  of  contamination. 

1  Spitzer   and   Epple,    Bitterness    in    Evaporated    Milk,    Journal    of    Dairy 
Science,  Vol.   III.,   1920. 

2  Lawrence    and   Laubach,    Studies    on    Aerobic,    Spore-bearing,    Non-path- 
ogenic Bacteria,  Journal  of  Bacteriology,  Vol.  I.,  p.  493. 


266  UNSWEETENED  CONDENSED  MILK  DEFECTS 

Blown  Evaporated  Milk  (Gaseous  Fermentation). 

General  Description. — The  ends  of  the  cans  bulge  out  very 
noticeably,  frequently  so  much  so  that  the  seams  of  the  cans 
burst  open.  This  is  due  to  gaseous  fermentation  causing  high 
pressure  in  the  cans.  The  pressure  is  often  so  great  that  upon 
opening  the  cans,  most  of  the  contents  are  blown  out  with  tre- 
mendous force.  In  some  cases  of  blown  evaporated  milk,  the 
contents  have  an  acid  odor,  pleasant  and  aromatic.  In  most 
instances,  however,  they  give  off  very  foul  odors  and  suggesting 
hydrogen  sulfide,  not  unlike  aggravated  cases  of  Limburger 
cheese.  These  odors  are  exceedingly  penetrating  and  difficult  to 
remove  from  anything  they  come  in  contact  with. 

Causes  and  Prevention. — The  bacteria  causing  gaseous  fer- 
mentations in  evaporated  milk  usually  belong  to  the  anaerobic 
group  of  butyric  acid  species  and  in  most  cases,  though  not  al- 
ways, the  putrefactive  types  prevail,  such  as  Bacillus  putrificus, 
Plectridium  novum  and  Plectridium  foetidum,  especially  the  lat- 
ter, because  of  its  extraordinary  power  of  resistance  to  heat. 
Plectridium  foetidum  is  an  obligatory  anaerobe  and  it  absolutely 
refuses  to  grow  under  aerobic  conditions.  It' is  an  actively  motile, 
medium-sized  organism  with  flagella  and  spores.  At  one  end  it 
has  an  Indian  club-like  enlargement,  in  which  appears  the  spore. 
The  bacillus  resembles  a  kettle-drum  stick  similar  to  B.  tetani. 
Under  strictly  anaerobic  conditions,  and  incubated  at  90  degrees 
F.,  it  ferments  milk  in  four  days.  The  milk  first  curdles,  then 
gradually  the  curd  dissolves  (digests)  completely,  leaving  a  clear 
yellow  liquid,  similar  in  appearance  to  butter  oil.  The  fermenta- 
tion is  accompanied  by  the  evolution  of  a  penetrating  foul  odor. 
This  organism  survives  exposure  for  15  minutes  to  245  degrees 
F.  Its  thermal  death  point  lies  between  245  and  250  degrees  F.1 

Plectridium  foetidum,  as  well  as  most  of  the  other  species  of 
anaerobic,  spore-bearing  butyric  acid  bacilli  and  bacteria,  is 
present  abundantly  in  cultivated  soil,  in  field  crops  and  even  on 
the  kernels  of  the  grain.  Since  this  type  of  evaporated  milk 
defect  is  characteristic,  especially,  of  the  product  manufactured 
during  the  late  summer  and  early  fall  months,  it  is  very  probable 
that  the  dust  incident  to  the  harvesting  of  the  field  crops,  fur- 


Hunziker,  A  Study  of  Gaseous  Fermentation   in  Evaporated  Milk. 


CONDENSED  MILK 


267 


nishes  the  chief  source  of  contamination  of  the  milk,  though  it 
is  quite  possible  that  contamination  with  these  germs  may  also 
result  from  the  use  of  unclean  equipment  in  the  factory. 

In  order  to  avoid  the  occurrence  of  blown,  fermented,  evapo- 
rated milk,  therefore,  it  is  necessary  to  employ  the  highest  steriliz- 
ing temperatures,  or  the  longest  exposure  to  the  sterilizing  heat, 
or  both,  consistent  with  freedom  of  the  milk  from  curdiness.  Ex- 
perience has  shown  that  the  use  of  the  ranges  of  temperature  and 


Pig- 


The  result  of  gaseous 
fermentation 


Fig*.  89.  Flectridinm  foetidum, 
a  highly  resistant  species  of 
anaerobic  micro-organisms, 
causing  "swell  heads"  of 
evaporated  milk 


time  of  exposure,  given  under  Chapter  XI  on  "Sterilizing,"  guard 
effectively  against  this  defect. 

Blown  Evaporated  Milk  Due  to  Freezing. — If  the  evapo- 
rated milk  is  exposed  to  storage  temperatures  below  the  freezing 
point  of  Water,  the  contents  of  the  cans  will  freeze.  While  freez- 
ing, the  contents  expand  sufficiently  to  cause  the  ends  of  the  cans 
to  bulge.  When  the  cans  are  subsequently  transferred  to  warmer 
temperatures,  so  that  their  contents  melt  again,  the  milk  contracts 
and  the  cans  resume  their  normal  shape. 

While  the  wholesomeness  and  flavor  of  the  product  are  not 
affected  by  the  freezing  process,  the  remelted  evaporated  milk 
is  usually  less  smooth  and  often  slightly  grainy.  This  is  due  to 
the  fact  that,  during  the  process  of  freezing,  there  is  a  partial 
separation  of  the  watery  portion  from  the  caseous  material.  The 
casein  contracts  and  the  watery  portion  freezes.  When  melted, 
the  emulsion  is  less  complete  than  it  was  before  freezing.  The 


268  UNSWESTDNSD  CONDENSED  MILK 

casein  remains  in  its  contracted  form  and  robs  the  product  of  its 
original  smoothness. 

Blown  Evaporated  Milk  Due  to  Chemical  Action. — While 
properly  processed  evaporated  milk  is  perfectly  sterile,  and  from 
the  biological  point  of  view,  keeps  indefinitely,  the  cans  of  very 
old  evaporated  milk  may  bulge,  as  the  result  of  the  action  of  the 
acid  in  the  milk  on  the  container.  Evaporated  milk  contains 
from  .35  to  .50  per  cent  acid  (calculated  as  lactic  acid).  When 
the  tin  cans  are  filled  Avith  the  evaporated  milk,  the  tinplate  is 
bright  and  untarnished,  both,  inside  and  out..  After  the  sterilizing 
process,  the  inside  surface  of  the  cans  is  dark  and  dull.  This  is 
caused  by  the  combined  action  of  acid  and  heat,  which  seems  to 
weaken  the  tinplate.  This  phenomenon  is  further  illustrated  by 
the  fact  that  where- creameries  pasteurize  their  skimmilk  and 
return  it  to  the  patrons  in  the  milk  cans  hot,  the  milk  cans  are 
short-lived;  they  soon  corrode  and  begin  to  leak. 

The  acid  in  the  evaporated  milk  continues  to  act  011  the  tin- 
plate  of  the  can  after  manufacture  and  in  the  case  of  very  old 
evaporated  milk,  the  acid  may  decompose  a  considerable  part  of 
thje  iron.  This  action  is  accompanied  by  the  evolution  of  hydro- 
gen gas,  which  causes  the  cans  to  bulge.  This  action  is  hastened 
by  continued  exposure  of  the  goods  to  high  temperatures  (sum- 
mer heat).  This  fact  was  experimentally  demonstrated,1  also, 
by  scratching  the  bottom  of  tin  cans  on  the  inside  with  a  file, 
then  filling  the  cans  with  a  .4  per  cent  solution  of  lactic  acid  and 
acetic  acid,  respectively.  After  sealing,  the  cans  were  sterilized 
in  the  autoclave,  so  as  to  avoid  any  possibility  of  bacterial  action. 
After  cooling,  these  sterilized  cans  were  incubated  for  some  time 
at  90  degrees  F.  The  cans  containing  the  dilute  acid  began  to 
swell,  while  the  check  cans,  containing-  distilled  water  only, 
remained  normal. 

Blown  Evaporated  Milk  Due  to  Change  in  Altitude. — Cans 
of  evaporated  milk  when  filled  in  factories  located  at  a  low 
altitude  (near  the  sea  level)  may  bulge  when  transferred  to  a  high 
altitude.  The  danger  from  this  source  is  intensified,  if  the  evap- 
orated milk  happens  to  be  cold  at  the  time  of  filling,  and  when  the 


1  Hunziker   and   Wright,    Indiana   Agricultural    Experiment    Station.      Re- 
sults not  published, 


CONDENSED  MILK  DEFECTS  269 

temperature  to  which  the  cans  are  exposed  at  the  high  altitude 
is  high. 

This  type  of  swelled  cans  obviously  has  nothing  to  do  with 
the  quality  of  the  contents,  nor  is  it  the  result  of  fermentation  or 
chemical  changes.  It  is  caused  by  the  fact  that  the  pressure  in 
a  can  sealed  at  the  sea  level  is  somewhat  greater  than  the  atmos- 
pheric pressure  surrounding  the  can  when  transferred  to  a  high 
altitude.  If,  at  the  same  time,  the  milk  packed  at  the  sea  level 
goes  into  the  can  at  a  low  temperature  and  the  atmospheric 
temperature  at  the  high  altitude,  to  which  the  sealed  cans  are 
shipped,  happens  to  be  high,  the  difference  in  pressure  between 
the  interior  and  exterior  of  the  can  is  further  increased,  due  to 
the  expansion  of  the  milk  and  of  the  air  in  the  can.  The  com- 
bination of  these  factors  is  sufficient  to  cause  the  ends  of  the  can 
to  bulge,  making  it  erroneously  appear  that  the  package  contains 
fermented  goods. 

This  has  actually  happened  in  the  case  of  one  factory  filling 
a  Government  war  contract,  the  whole  shipment  of  evaporated 
milk  being  rejected  by  the  Government,  because  of  the  bulged 
cans. 

Occurrences  of  this  type  can  be  prevented  by  filling  cans, 
intended  for  markets  in  high  altitudes,  with  the  evaporated  milk 
while  warm. 

Brown  Evaporated  Milk. 

General  Description. — It  is  the  aim  of  the  processor  to  so 
govern  the  sterilizing  process  as  to  give  the  evaporated  milk  a 
rich,  yellow;  creamy  color.  Frequently,  this  color  limit  is  over- 
stepped to  the  extent  of  imparting  to  the  evaporated  milk  a  brown 
color,  suggesting  coffee  with  milk  in  it.  In  this  condition  evap- 
orated milk  fails  to  appeal  to  the  consumer. 

Causes  and  Prevention. — The  dark  color  in  evaporated  milk 
is  due  to  the  oxidizing  action  of  excessive  heat  on  the  milk  sugar, 
causing  the  milk  sugar  to  caramelize.  This  can  be  avoided  by 
reducing  the  sterilizing  temperature,  or  shortening  the  sterilizing 
process,  or  both.  The  storing  of  evaporated  milk  at  high  temper- 
atures (summer  heat)  also  tends  to  deepen  its  color  with  age. 


270  UNSWEETENED  CONDENSED  MILK  DEFECTS 

Gritty  Plain  Condensed  Bulk  Milk. 

General  Description. — Grittiness  in  the  unsweetened  goods 
appears  usually  only  in  the  plain  condensed  bulk  milk.  It  is  a 
defect  which  renders  the  product  undesirable  for  ice  cream 
making. 

Causes  and  Prevention. — The  chief  cause  of  this  defect  is 
too  great  concentration.  Plain  condensed  bulk  milk  which  is  not 
condensed  over  3.5  parts  of  fresh  milk  to  1  part  of  condensed  milk 
does  not  become  gritty.  When  the  concentration  exceeds  4:1, 
the  milk  sugar  begins  to  crystallize  out,  making  the  product 
gritty.  Milk  sugar  requires  about  six  times  its  weight  of  water 
for  complete  solution  in  cold  water.  When  condensed  at  the 
ratio  of  4:1  or  over,  the  plain  condensed  bulk  milk  contains  con- 
siderably less  than  five  parts,  by  weight,  of  water  to  one  part 
of  milk  sugar.  This  high  concentration,  together  with  the  prac- 
tice of  storing  this  product  at  refrigerating  temperatures  in  order 
to  preserve  it,  is  responsible  for  the  grittiness.  This  trouble  can, 
therefore,  easily  be  prevented  by  not  condensing  to  quite  as  high 
a  degree  of  concentration. 

Metallic  Evaporated  Milk  and  Plain  Condensed  Bulk  Milk. 

General  Description. — Both,  evaporated  and  plain  condensed 
bulk  milk  may  show  a  metallic  and  puckery  flavor,  though  this 
defect  is  rather  rare. 

Causes  and  Prevention. — The  metallic  flavor  may  be  due 
to  the  same  cause  as  metallic  sweetened  condensed  milk,  i.  e.,  an 
unsanitary  condition  of  the  vacuum  pan,  in  which  case  its  recur- 
rence can  be  readily  avoided  by  thoroughly  cleaning  all  parts  of 
the  pan  including  the  dome  and  the  goose  neck,  and  rinsing  down 
the  whole  pan  thoroughly  with  clean  water  each  morning  before 
operations  begin. 

Unsweetened  condensed  milk  made  by  the  use  of  the  "Con- 
tinuous Concentrator"  may  have  a  metallic  flavor  when  the 
scrapers  in  this  machine  are  improperly  adjusted,  causing  them 
to  cut  into  the  copper  walls  and  thereby  incorporating  metallic 
copper  in  the  product.  This  source  of  metallic  flavor  can  be 
removed  by  proper  adjustment  of  the  revolving  spider  and  its 
essential  parts. 


ADULTERATIONS  OF  CONDENSED  MILK  271 

Evaporated  milk  may  also  show  a  metallic  flavor  as  the  result 
of  chemical  action  of  the  acid  in  the  milk  on  the  can.  This  occurs 
usually  only  upon  prolonged  storage.  Very  old  evaporated  milk 
is  very  prone  to  have  a  metallic  flavor  from  this  source  and 
particularly  when  stored  at  a  rather  high  temperature.  This  can 
best  be  avoided  by  endeavoring  to  move  the  goods  sufficiently 
rapidly  to  limit  the  age  of  the  milk  to  a  reasonable  period  of  time 
and  by  avoiding  high  storage  temperatures. 

Cans,  in  the  manufacture  and  sealing  of  which  an  acid  flux 
is  used,  are  prone  to  give  the  contents  a  puckery,  metallic  flavor, 
due  to  the  zinc  chloride  and  hydrochloric  acid  present.  This  can 
be  avoided  by  using  cans  only  in  the  manufacture  of  which  a 
non-acid  flux,  such  as  gasoline-resin  flux,  is  used,  and  by  using 
a  non-acid  flux  for  sealing  the  filled  cans. 

CHAPTER  XXTV. 
ADULTERATIONS  OF  CONDENSED   MILK. 

It  is  the  sense  of  the  Federal  Pure  Food  Act  that  the  addition 
to  condensed  milk  of  any  substance  except  sucrose,  and  the 
abstraction  of  any  substance  from  milk  except  water,  is  an 
adulteration. 

Skimming. — Condensed  milk  made  from  partly  or  wholly 
skimmed  milk  must  be  labeled  and  sold  as  condensed  skimmed 
milk  in  order  to  comply  with  the  Pure  Food  regulations.  How- 
ever, it  is  possible  for  condenseries  receiving  fresh  milk,  rich 
in  butter  fat,  to  skim  a  part  of  that  milk  and  have  their  product 
still  conform  with  the  food  standards. 

Skimmed  sweetened  condensed  milk  can  readily  be  detected 
by  its  whitish  color,  while  condensed  whole  milk  has  normally 
a  rich  yellow  color.  When  diluted,  to  the  consistency  of  ordi- 
nary milk,  skimmed  condensed  milk,  both  the  sweetened  and  the 
unsweetened,  foams  very  profusely  when  shaken,  while  diluted 
condensed  whole  milk  behaves  similar  to  ordinary  whole  milk.1 

Addition  of  Artificial  Fats. — In  order  to  lo\ver  the  cost  of 
manufacture,  attempts  have  occasionally  been  made  to  skim  the 

1  For  chemical  tests  of  butter  fat  in  condensed  milk  see  Chapters  XXXI 
and  XXXII. 


272  ADULTERATIONS  OF  CONDENSED  MILK 

fresh  milk  and  substitute  the  abstracted  fat  by  artificial  fats  of 
animal  or  vegetable  origin. 

Recent  improvements  in  the  method  of  manufacture  have 
made  it  possible  to  manufacture  evaporated  milk,  made  from 
skim  milk  to  which  foreign  fats,  especially  vegetable"  oils,  such 
as  cocoanut  oil,  have  been  added.  This  milk  has  every  appear- 
ance of,  and  will  commercially  keep  as  well  as  genuine  evaporated 
milk.  A  representative  of  this  imitation  evaporated  milk  is  the 
"Hebe"  product.  This  product  consists  of  skim  milk  to  which 
have  been  added  vegetable  fats  to  replace  the  butter  fat.  The 
mixture  is  homogenized  in  order  to  form  a  complete  emulsion, 
then  it  is  evaporated,  filled  in  cans  and  sterilized  in  a  similar 
manner  as  the  genuine  evaporated  milk. 

The  Federal  law  requires  that  the  composition  and  ingredi- 
ents of  these  imitation  products  appear  plainly  on  the  label  of  the 
package. 

It  should  be  clearly  understood  by  the  manufacturer,  the 
dealer  and  the  consumer  that  this  imitation  milk  is  inferior  to 
the  genuine  evaporated  milk,  in  the  fact  that  it  lacks  the  im- 
portant growth-promoting  and  curative  properties  which  are 
inherent  in  whole  milk.  If  sold  on  its  owin  merits,  and  in  accord- 
ance with  the  'Federal  law,  there  can  be  no  logical  objection  to 
the  imitation  product,  but  if  offered  to  the  consumer  as  the 
genuine  article,  the  manufacture  and  sale  of  imitation  evaporated 
milk  is  a  heinous  crime  against  humanity. 

Experiments  conducted  at  Ohio  State  University,  by  Mr. 
J.  L.  Hutchison,  instructor  in  the  Department  of  Agricultural 
Chemistry  under  the  direction  of  Professor  O.  Erf,  Chief  of 
Department  of  Dairy  Husbandry  and  Dr.  J.  F.  Lipman,  Professor 
of  Agricultural  Chemistry,  demonstrated  that  "Hebe"  milk,  when 
fed  to  young  white  rats,  resulted  in  malnutrition  accompanied 
by  stunted  growth,  sore  eyes  and  death  of  some  of  the  experi- 
mental rats,  in  a  similar  manner  as  did  other  rations  in  which 
the  fat  soluble  vitamines  were  lacking. 

The  volume  of  "filled"  evaporated  milk  manufactured  in  this 
country  is  assuming  large  proportions  and  is  growing  annually 
as  shown  below: 


ADULTERATIONS  OF  CONDENSED  MILK 


273 


Annual    Output    of    Imitation    Evaporated    Milk,    Made    from 

Wholly  or   Partly   Skimmed  Milk  to  Which  Foreign  Fats 

had  been  Added.1 


Year 

Case   Goods 
Pounds 

Bulk   Goods 
Pounds 

Total 
Pounds 

1916 

12000 

14  134712 

14,146,712 

1917  
1918  

18,504 
41,033,855 

17,487,064 
7,591,182 

17,505,568 
48,625,037 

1919  

62,262,221 

2,748,120 

65,010,341 

Mothers  who  buy  evaporated  milk  for  feeding  infants  and 
children  should  be  cautioned  to  observe  carefully  whether  or  not 
they  receive  the  genuine  article.  Imitation  evaporated  milk  is 
not  a  baby  food.  Babies  and  growing  children  need  butterfat 
for  their  best  development.  Tf  canned  milk  is  used  for  infant 
feeding,  it  should  be  made  from  whole  milk  only.  (See  also 
Chapter  XX  on  "Vitamine  Properties  of  Condensed  Milk.") 

Addition  of  Commercial  Glucose. — Commercial  glucose  be- 
longs to  a  group  of  starch  products  in  which  dextrose  is  the 
leading  constituent.  It  is  manufactured  by  the  action  of  dilute 
acids  in  starch  and  starchy  matter,  or  occasionally  woody  fibre. 
In  this  country  it  is  almost  wholly  made  from  maize  starch. 

Starch  glucose  occurs  in  commerce  in  several  forms,  varying 
from  the  condition  of  pure  anhydrous  dextrose,  through  inferior 
kinds  of  solid  sugar,  to  the  condition  of  a  thick  syrupy  liquid, 
colorless  and  transparent,  resembling  molasses  in  consistency 
and  glycerine  in  appearance;  it  contains  a  large  proportion  of 
dextrin.  In  connection  with  the  manufacture  of  condensed  milk 
the  term  "glucose"  refers  to  this  thick,  syrupy  liquid.  It  is  added 
to  the  condensed  milk  with  a  view  of  substituting  a  portion  of 
the  sucrose  and  thus  reducing  the  cost  of  manufacture.  It  has 
also  been  suggested  that  the  presence  of  commercial  glucose  in 
condensed  milk  prevents  the  precipitation  of  sugar  crystals.  Ex- 
periments have  shown,  however,  that  condensed  milk  containing 
varying  amounts  of  glucose,  will  become  sandy  just  as  readily 
as  normal  condensed  milk. 

That  glucose  cannot  be  used  as  a  substitute  for  sucrose,  is 


The  Market  Reporter,  U.  S.  Bureau  of  Markets,  Vol.  I,  No.  18,  1920. 


274  ADULTERATIONS  OF  CONDENSED  MILK 

obvious  from  the  fact  that  its  presence  defeats  the  very  object 
for  which  sucrose  is  added.  Instead  of  serving  as  a  preservative, 
as  is  the  case  with  the  best  refined,- granulated  cane  sugar,  glucose 
acts  as  a  most  effective  fermentative.  It  has  been  explained  that 
the  presence  in  sucrose  of  traces  of  invert  sugar,  or  levulose  and 
glucose,  causes  condensed  milk  to  ferment.  Glucose  belongs  to 
the  monosaccharides.  Its  chemical  formula,  like  that  of  levulose, 
is  C6H12O6,  it  oxidizes  readily  and  iinder  the  influence  of  yeast 
and  other  micro-organisms  it  ferments,  yielding  mainly  alcohol 
and  carbon  dioxide.  Its  presence  in  condensed  milk,  therefore, 
is  prone  to  start  fermentation,  and  the  manufacturer  who  uses 
it  with  a  view  of  lessening  the  cost  of  manufacture  of  condensed 
milk  is,  indeed,  practicing  poor  economy.  There  is  no  adultera- 
tion of  sweetened  condensed  milk  that  will  produce  such  in- 
evitable disaster  as  the  addition  to  it  of  glucose.  Aside  from  this 
fact,  the  law  prohibits  the  addition  of  anything  except  sucrose. 

Addition  of  Bi- Carbonate  of  Soda,  Ammonium  Hydroxide, 
Lime  Oxide  and  Lime  Hydrate  and  Other  Alkali. — These  alkalies 
and  alkaline  earths  are  frequently  added  to  evaporated  milk,  for 
the  purpose  of  neutralizing  excess  of  acid,  or  balancing  the  ash 
constituents,  in  order  to  diminish  the  viscosity  and  tendency  to 
curdle,  to  facilitate  the  sterilizing  process,  and  to  prevent  the 
milk  from  curdling  when  exposed  to  heat.  If  used  in  reasonable 
quantities,  they  interfere  in  no  way  with  the  quality  and  health- 
fulness  of  the  product,  and  may  in  exceptional  cases  prevent 
great  loss.  If  used  in  excess,  the  milk  will  foam,  very  badly  in 
the  vacuum  pan,  which  renders  the  process  of  condensing  a  diffi- 
cult one  and  the  finished  product  has  a  bitter  flavor.  Under 
ordinary  conditions,  their  use  is  entirely  unnecessary  and  simply 
means  additional  labor  and  expense.  The  above  agents  and  also 
viscogen,  are  sometimes  used  with  the  view  of  thickening  sweet- 
ened condensed  milk  and  increasing  the  output.  Experimental 
results,1  however,  showed  that  these  agents  cannot  be  used  in 
large  enough  quantities  to  produce  the  above  results  without 
materially  lowering  the  quality  of  the  product. 

Addition  of  Cream  of  Tartar. — Cream  of  tartar  is  used  ex- 
tensively in  the  manufacture  of  candies  and  caramels.  Its  purpose 


1  Hunziker,  experiments  not  published. 


ADULTERATIONS  OF  CONDENSED  MILK  275 

is  to  make  the  sugar  in  these  products  precipitate  in  the  form  of 
very  fine  and  soft  crystals.  Condenseries,  which  have  been  con- 
tinually troubled  with  sugar  crystallization  and  sugar  sediment, 
have  tried  to  overcome  this  defect  by  adding  cream  of  tartar  to 
the  sweetened  milk  in  the  vacuum  pan.  Cream  of  tartar  is  an 
acid  salt  (acid  potassium  tartrate,  KH.C4H4O6),  and  it  is  this 
acid  which  in  the  manufacture  of  candy  causes  the  fine  and  soft 
grain  of  the  sugar.  It  is  obvious  that  if  enough  cream  of  tartar 
were  added  to  condensed  milk  to  produce  the  desired  effect  on 
the  sugar,  the  acid  present  would  curdle  the  milk.  Its  use  is  of 
no  value  to  the  manufacturer  of  condensed  milk. 

Addition  of  Starch. — The  pasty  and  thick  consistency"  of 
sweetened  condensed  milk  frequently  suggests  to  the  public  that 
it  contains  starch.  This  is  erroneous,  for  it. is  doubtful  if  con- 
densed milk  is  ever  adulterated  with  starch.  There  would  be 
nothing  gained  by  so  doing,  and  the  presence  of  starch  in  con- 
densed milk  could  be  readily  detected  with  iodine.  Iodine  gives 
the  starch  cells  a  deep  blue  color. 


PART  VI. 
MANUFACTURE  OF   MILK  POWDER 

CHAPTKR  XXV. 
DEFINITION. 

Milk  powder,  dry  milk,  pulverized  milk,  dehydrated  milk, 
desiccated  milk,  milk  flour,  is  made  from  cow's  whole  milk,  or 
partly  or  wholly  skimmed  milk,  or  from  whole  milk  that  has  been 
enriched  by  additional  butterfat,  to  which  sugar,  or  alkalies,  or 
both  may,  or  may  not  have  been  added,  and  which  has  been 
evaporated  to  dryness,  either  under  atmospheric  pressure,  or 
in  vacuo.  Powders  made  from  cream  containing  18  per  cent 
butterfat  or  more,  are  called  cream  powders. 

KINDS. 

The  milk  powders  on  the  market  vary  chiefly  in  their  solu- 
bility and  fat  content.  The  bulk  of  the  milk  powders  is  produced 
from  wholly  or  partly  skimmed  milk.  Most  of  the  milk  powders 
of  the  early  days  of  this  industry  contained  added  cane  sugar 
and  alkalies.  The  purpose  of  the  addition  of  alkalies  was  to 
lend  greater  solubility  to  the  proteids. 

The  process  of  manufacture,  however,  has  been  improved 
to  the  extent  to  where  the  solubility  of  the  proteids  can  now 
be  preserved  without  the  admixture  of  alkalies.  Most  of  the 
milk  powders  put  on  the  market  in  this  country  are  free  from 
admixture  of  any  substances  foreign  to  normal  milk. 

HISTORY  AND   DEVELOPMENT  OF  INDUSTRY. 

The  origin  and  history  of  the  milk  powder  industry  are  very 
closely  related  and  intimately  connected  with  those  of  the  con- 
densed milk  industry.  The  fundamental  purpose  of  the  two 
products  is  one  and  the  same,  i.  e.,  to  preserve  milk  as  nearly 
as  possible  in  its  natural  condition,  and  to  reduce  its  bulk  to  the 
minimum,  so  as  to  make  possible  its  economical  transportation 
to  all  parts  of  the  world. 


MANUFACTURE  OF  MILK  POWDER  277 

The  difference  between  milk  powder  and  condensed  milk 
is  mainly  one  of  degree  of  concentration.  It  is  not  surprising, 
therefore,  that  the  inventions  .of  processes  of  manufacture  of  the 
two  products  date  back  to  about  the  same  period,  the  middle  of 
last  century,  and  in  most  cases  the  inventors  of  the  one  product 
had  also  in  mind  and  gave  due  consideration  to  the  possibilities 
of  the  other. 

The  first  commercially  usable  process  was  invented  by 
Grimwade  who  secured  a  patent  from  the  British  Government 
in  1855.  His  process  consisted  briefly  of  first  adding  carbonate 
of  soda  or  potash  to  the  fresh  milk,  then  evaporating  in  open 
jacketed  pans  and  with  constant  agitation.,  until  a  dough-like 
substance  was  obtained;  then  adding  cane  sugar;  the  mixture 
was  then  pressed  between  rollers  into  ribbons,  further  dried 
and  then  pulverized.  The  alkali,  in  the  form  of  carbonate  of 
soda  or  potash,  was  added  in  order  to  render  the  casein  more 
soluble,  and  the  purpose  of  the  admixture  of  the  sugar  was  to 
produce  granulation  of  the  dough  toward  the  end  of  the  process 
facilitating  the  removal  of  moisture  during  the  later  stages  of  the 
drying  process.  The  evaporation  in  open  pans  was  later  super- 
seded by  the  use  of  the  vacuum  pan.  The  Grimwade  process  of 
manufacturing  milk  powder  w'as  in  practice  for  some  years. 

Since  the  introduction  of  the  Grimwade  process,  several 
modifications  thereof  have  been  patented,  and  numerous  new 
processes  for  desiccating  milk,  that  involve  principles  entirely 
different  from  the  Grimwade  process,  have  been  invented,  have 
found  wide  commercial  application  and  have  practically  super- 
seded the  use  of  the  earlier  inventions. 

The  perfection  of  processes  suitable  for  the  commercial 
manufacture  of  dried  milk  is  of  relatively  recent  origin  and  dates 
back  largely  to  the  closing  years  of  the  nineteenth  century  and 
the  first  decade  of  the  twentieth  centry.  Up  to  that  time  the 
annual  output  of  milk  powder  was  comparatively  small.  But 
within  the  last  score  of  years  rapid  progress  has  been  made  and 
the  world  war  has  lent  this  industry  additional  impetus.  Today 
the  annual  production  is  assuming  large  proportions,  especially 
that  of  powdered  skim  milk,  though  considerable  quantities  of 
powdered  whole  milk,  powdered  cream  and  powdered  buttermilk 
are  also  manufactured,  as  shown  below. 


278  MANUFACTURE  OF  MILK  POWDER 

Annual  Production  of  Skim  Milk  Powder,  Whole  Milk  Powder 
and  Cream  Powder  in  the  United  States.1 


Pounds 

3  by  Years 

1918 

1919 

Skim  milk  powder  

25,432,007 

33,076,131 

\Vhole  milk  powder 

4  164  334 

8  660  78S 

Cream  powder     

654  360 

592  070 

According  to  Potts,2  the  number  of  firms  manufacturing 
powdered  milk  products  in  the  United  States  is  as  follows : 

Skim   milk  powder 47 

Whole    milk    powder 15 

Cream  powder   ". 3 

Description  of  the  Principal  Processes  of  Manufacture. 

The  processes  of  desiccating  milk,  which  have  proven  com- 
mercially successful  and  have  found  wide  application,  may  be 
conveniently  grouped  into  three  fundamental  categories,  accord- 
ing to  the  predominating  principle  upon  which  they  are  based. 
These  are: 

1.  Dough-drying  processes. 

2.  Film-drying  processes. 

3.  Spray-drying  processes. 

For  detailed  discussion  of  the  more  outstanding  principles 
covered  in  some  of  the  patents  of  these  processes  the  reader  is 
referred  to  the  following  brief  description  and  illustrations. 

1.    Dough-drying  Processes. 

To  this  group  largely  belong  the  earlier  and  cruder  pro- 
cesses. The  milk  is  condensed  in  any  manner,  either  by  heating 
in  open  pans  under  atmospheric  pressure  and  usually  with  the 
help  of  mechanical  agitation ;  or  in  the  vacuum  pan  with  or  with- 
out mechanical  agitation;  or  in  open  vats  by  blowing  heated 
air  through  the  milk,  to  a  high  degree  of  concentration  and  to 
a  dough-like  consistency.  The  concentrated  product  is  then 

i  The  Market  Reporter,  U.  S.  Bureau  of  Markets,  Vol.  I.,  No.  14,  1920. 
9  Potts.     Data  furnished  by  correspondence.     1920. 


MANUFACTURE  OF  MILK  POWDER 


279 


spread  on  trays  or  other  similar  containers,  and  dried  to  a  hard 
substance  in  vacuum  chambers  or  in  other  vaults  or  drying  ap- 
paratus, provided  with  heating  devices  or  currents  of  hot  air. 
The  dried  product  is  subsequently  ground  to  a  fine  powder. 
Examples  of  this  type  of  milk-drying  processes  are  the  Wimmer 
process,  the  Campbell  process  and  others. 

The  Wimmer  Process.  —  The  milk 
is  boiled  in  a  vacuum  pan  similar  to 
that  used.  in  the  manufacture  of  con- 
densed milk.  The  vacuum  pan  has  a 
deep  steam  jacket  for  heating,  but  in 
the  place  of  the  usual  coils,  the  pan  is 
equipped  with  a  mechanical  stirrer. 
The  milk  is  condensed  at  a  relatively 
low  temperature  and  the  stirrer  re- 
volves until  the  water  content  of  the 
milk  is  reduced  to  about  30  per  cent 
and  the  milk  has  become  porous  and 
crumbly,  though  it  still  forms  a  com- 
pact mass.  The  drying  is  then  com- 
pleted in  the  open  air  and  without  addi- 
tional heating.  The  product  is  then 
ground  to  a  powder.  This  is  the  pro- 

cess  invented  by  Ole  Bul1  Wimmer  of 
Copenhagen,  Denmark. 

The  Campbell  Process.  —  This  process  was  invented,  pat- 
ented and  improved  by  J.  H.  Campbell  of  New  York  City,  U.  S. 
patent  Nos.  668,159  and  668,161,  February  19,  1901  ;  U.  S.  patent 
No.  718,191,  January  13,  1903;  U.  S.  patent  No.  762,277,  June 
14,  1904;  and  by  J.  H.  and  H.  C.  Campbell,  U.  S.  patent  No. 
668,162,  February  19,  1901;  and  by  C.  H.  and  P.  T.  Campbell, 
U.  vS.  patent  No.  771,609,  October  4,  1904. 

The  Campbell  process  consists  essentially  of  concentrating 
milk  to  a  high  degree  of  concentration  by  blowing  heated  air 
through  it  in  an  open  vat.  The  milk  is  reduced  to  a  very  thick 
consistency,  resembling  a  batter.  The  concentrated  milk  is  then 
removed  from  the  evaporating  tank,  is  reduced  mechanically  to 
small  units  by  means  of  a  pugging  or  shredding  machine,  or 


Fifir' 


280 


MANUFACTURE:  OF  MILK  POWDKR 


otherwise.  This  subdivided  product  is  then  placed  on  shelves 
or  trays  and  dried  in  a  chamber  heated  to  a  temperature  below 
the  coagulating  point  of  the  albumen. 


Pig-.  91.     The  Campbell  milk  drier 


I.  A  concentrating  vessel,  a  outlet,  b  valve,  c  hot  water  jacket,  c1  hot 
water  pipe,  c2  discharge  of  jacket,  B  air  pipe,  e  connecting  hose,  f  stand  pipe, 
g  air-distributing  disc,  t  air  chamber. — II.  E  pug  mill,  i  cylinder,  j  hopper, 
k  chute,  1  horizontal  shaft,  m  blades  for  stirring,  m'  projections  for  scraping 
blades,  P  Vermicelli-machine,  n  hopper,  o  cylindrical  chamber,  p  piston,  q 
spiral  screw,  q'  worm-wheel,  o'  small  holes,  .ri  endless  traveling  apron,  s  tray 
with  perforated  bottom. — III.  G  drier,  t  body  of  drier,  H  blower,  t'  flue,  u 
opening  to  insert  trays,  u'  opening  for  removing  trays,  vv  endless  chains  with 
projections  for  supporting  trays,  w  coil  heater,  w'  pipe  circulating  hot  water. 

In  the  processes  of  the  dough-drying  principle  of  desiccation, 
the  dried  product  is  reduced  to  a  marketable  powder  by  grinding 
it  and  then  bolting  or  or  sifting  it. 

2.    Film-Drying  Processes. 

To  this  group  belong  the  numerous  processes  in  which  the 
milk,  with  or  without  previous  concentration,  is  dried  on  the 
surface  of  one  or  more  steam-heated,  revolving  drums.  The 
milk  is  either  picked  up  by  the  revolving  drums,  or  it  is  sprayed 
onto  these  drums,  forming  aMhin  film  which  dries  rapidly.  The 
film  of  dried  milk  so  formed  is  atomatically  removed  with  each 
revolution  of  the  drum  by  means  of  a  mechanical  scraper.  In 
some  of  the  processes  of  the  film-drying  type  the  drying  cyl- 
inders operate  in  the  open,  under  atmospheric  pressure,  in  others 


MANUFACTURE  OF  MILK  POWDER 


281 


the  drying"  drums  are  incased  in  a  vacuum  chamber  and  the 
drying  is  accomplished  under  reduced  pressure.  Some  of  the 
U.  S.  patents  of  tlie  film-drying  process  that  have  found  wide 
commercial  application  are  described  below. 

The  Just  Process. — This  process  appears  to  be  the  first  of 
its  type  that  found  wide  application  in  the  desiccating  of  milk. 
Tt  was  invented  and  patented  by  John  A.  Just  of  Syracuse,  New 
York,  U.  S.  patent  No.  712,545,  November  4,  1902. 


Fig1.  92.     The  Just  milk  drier 

The  essential  equipment  involved  in  the  Just  process  con- 
sists of  two  horizontal  steam-heated  revolving  metal  cylinders. 
These  cylinders  are  installed  sufficiently  close  to  each  other  so 
that 'there  is  contact  at  their  periphery.  A  milk  destributing  tank 
(7)  with  adjustable  discharge  (8  and  9)  in  the  center  over  and 
between  the  two  cylinders.  Scrapers  or  knives  (11)  which  re- 
move the  dried  film  of  milk  from  the  cylinders;  and  receptacles 
(12)  which  receive  the  finished  powder. 


282 


MANUFACTURE  OF  MILK  POWDER 


The  patent  claims  of  the  Just  process  cover  the  treatment 
of  the  milk  with  calcic  chloride  (Ca  O  +  Ca  C12),  or  with  the 
double  salt  of  sodium  and  calcium  citrate,  to  reduce  the  acidity 
of  the  milk,  and  with  alkaline  hypochlorite  for  the  purpose  of 
preserving  the  fatty  acids  in  the  finished  product,  the  heating 
and  boiling  of  the  milk  by  bringing  it  in  'contact  with  a  heating 
surface  of  a  temperature  above  212  degrees  F.  and  below  270 
degrees  F.,  allowing  the  thus  treated  and  heated  milk  to  flow 
in  regulated  quantities  on  the  surface  of  the  steam  heated  re- 
volving metal  cylinders,  where  it  is  dried  in  the  form  of  a  film 
and  from  which  it  is  removed  by  mechanical  scrapers.  The 
temperature  of  the  heating  surface  on  the  cylinders  is  to  exceed 
212  degrees  F.  and  to  be  below  270  degrees  F. 

The  high  temperature  to  which  the  milk  is  heated  obviously 
reduces  the  solubility  of  the  finished  powder.  The  purpose  of 
neutralizing  the  acidity  of  the  milk,  before  drying,  is  to  mini- 
mize the  solubility-destroying  action  of  the  high  heat. 

The  Hatmaker  Process. — This  is  similar  to  the  Just  process. 
James  R.  Hatmaker  of  London,  England,  purchased  the  Just 


rig-.  93.     The  Just-Hatmaker  milk  drier 

process  for  operation  in  Europe  and  later  secured  a  patent  of 
his  own,  which  represents  a  modification  of  the  original  Just 
process,  and  which  is  known  as  the  Just-Hatmaker  process. 


MANUFACTURE  OF  MII,K  POWDER 


283 


The  Gathmann  Process. — This  process  and  equipment  was 
invented  and  patented  by  •  Louis  Gathmann  of  Washington, 
D.  C.,  U.  S.  patent  No.  834,516,  October  30,  1906. 

In  this  process,  similar  as  in  the  Just  process,  the  milk  is 
dried  in  the  form  of  a  film  on  a  revolving,  steam-heated  drum, 
under  atmospheric  pressure.  In  this  case,  however,  only  one 
drum  is  used,  the  drum  (A)  is  cone-shape  instead  of  cylindrical 
and  its  surface  is  spirally  grooved  or  corrugated  (a)  and  the 
adjacent  surface  against  which  the  cone  revolves  is  also  similarly 
corrugated  but  the  spiral  grooves  (b1)  running  in  the  opposite 


Fig*.  94.     The  Gathmauu  milk  drier 

direction  from  those  on  the  cone,  as  is  common  in  grinding- 
mills.  Hence  when  the  cone  revolves  the  drying  milk  is  kneaded 
and  ground  between  the  two  surfaces  and  is  gradually  carried 
or  pushed  by  the  corrugated  surface  of  the  revolving  cone  to 
the  smaller,  or  discharge  end  of  the  machine. 

The  adjacent  corrugated  surface  against  which  the  surface 
of  the  cone  grinds,  and  which  incases  the  lower  half  of  the  surface 
of  the  cone,  is  steam  jacketed  (b2),  so  that  the  milk  is  between 
two  heated  surfaces. 

A  hopper  (D)  regulates  and  feeds  the  flow  of  the  milk  to 
the  cone  at  its  larger  end  and  a  brush  (G)  located  near  the 
smaller  end  of  the  cone  removes  such  parts  of  the  dried  milk 


284 


MANUFACTURE;  OF  MILK  POWDKR 


as  may  adhere  to  the  grinding  surface.  Baffle  boards  or  clash 
boards  are  provided  to  receive  such  of  the  milk  as  may  splash 
from  the  cone. 

The  patent  claim  covers  the  drying  of  the  milk  by  feeding 
it  to  a  continuously  moving,  heated  surface,  where  it  is  permitted 
to  form  a  comparatively  thin  layer,  heating  it  to  evaporate  the 
water,  and  simultaneously  subjecting  it  to  a  kneading,  which 
gradually  changes  to  a  grinding  action,  as  the  milk  solidifies, 
and  forms  a  powder. 

The  temperature  of  the  heating  surface  is  recommended  to 
be  that  of  boiling  water,  but  may  be  between  212  degrees  F.  and 
270  degrees  F.  The  milk  enters  the  hopper  without  preheating 
and  without  other  treatment. 

The    Passburg    Process. — This    process    was    invented    and 


Pig-.   95.     The  Passburg-  milk  drier 

patented  by  Emil  Passburg  of  Berlin,  Germany,  U.  S.  patent 
No.  726,742,  April  28,  1903.  This  film  dryer  operates  under 
reduced  pressure.  It  consists  of  an  outer  casing  (A)  in  which 
revolves  one  steam  heated,  metal  drum  (T),  an  automatic  milk 


MANUFACTURE:  OF  MILK  POWDER  285 

supply  regulating  feed  (E)  which  keeps  the  milk  in  the  vacuum 
casing  at  a  constant  level,  an  overflow  aperture  (J)  that  regulates 
the  thickness  of  the  film,  a  vacuum  pump,  a  scraper  (S)  to 
remove  the  film  of  dried  milk  from  the  revolving  drum  and  an 
evacuated  receiver  (B)  for  the  dried  substance. 

The  milk  is  drawn  into  the  drum  casing  or  vacuum  chamber 
by  the  force  of  the  vacuum  in  this  chamber.  By  the  proper 
adjustment  of  the  feed  valve  and  the  overflow  valve,  the  milk 
rises  to  a  given  level  and  stays  at  that  level  while  operation  is 
in  progress.  The  revolving  steam-heated  drum  slightly 
dips  into  the  milk  in  the  vacuum  chamber  and  picks  up  a  film 
of  milk  which  dries  under  reduced  pressure  while  the  drum 
makes  one  revolution.  The  dried  film  is  removed  by  the  auto- 
matic scraper  and  the  finished  dried  milk  is  discharged  into  the 
receiver,  while  the  moisture-laden  air  and  vapors  escape  through 
a  condenser  located  outside  of  the  drying  apparatus. 

The  Ekenberg  Process. — This  is  also  a  film  drier  operating 
in  vacuo.  This  process  was  invented  by  Martin  Ekenberg  of 
Stockholm,  Sweden,  in  the  year  1899  and  is  covered  by  a  number 
of  United  States  patents,  some  of  the  earlier  of  which  are  patent 
No.  764,925,  1904,  and  No.  785,600,  March  21,  1905.  The  patents 
covering  this  process  are  owned  by  the  Ekenberg  Company  of 
Cortland,  N.  Y.,  who  are  operating  numerous  milk  drying  fac- 
tories in  the  States  of  New  York  and  Michigan. 

The  Ekenberg  milk  drier  is  called  exsiccator.  It  consists 
of  a  revolving,  steam  heated  nickel  drum,  inclosed  in  a  vacuum 
chamber.  The  ends  of  the  drum  form  bell-shaped  bowls, 
dished  outward.  The  drum  is  equipped  with  knives  or.  scrapers, 
which  remove  the  film  of  dried  milk  that  gathers  on  the  drum. 
Attached  to  the  vacuum  chamber  there  is  a  smaller  chamber 
which  serves  to  receive  the  dried  milk  as  it  is  scraped  from  the 
drum.  This  is  separated  from  the  large  vacuum  chamber  by  a 
series  of  air  locks,  so  that  the  material  may  be  removed  without 
breaking  the  vacuum  in  the  large  chamber.  ' 

The  milk,  as  it  enters  the  vacuum  chamber,  is  sprayed  into 
the  concave  ends  of  the  drum.  In  this  manner  it  is  fore-con- 
densed. It  is  then  withdrawn  from  the  vacuum  chamber  by  a 
pump,  and  returned  again,  this  time  being  sprayed  upon  the 


286  MANUFACTURE  OF  MILK  POWDER 

periphery  of  the  drum.    The  milk  remains  on  the  drum  only  long 
enough  for  it  to  make  three-quarters  of  a  revolution. 

After  the  dried  milk  is  removed  from  the  exsiccator,  it  is 
placed  in  a  special  drying  chamber  at  a  temperature  of  90  degrees 
FX  where  it  remains  long  enough  for  the  milk  sugar  to  crystallize. 
This  is  usually  accomplished  in  about  an  hour.  After  this  it  is 
ground  and  sifted  in  a  similar  manner  as  is  the  case  in  the  milling 


Fig.  96.    The  Ekenberg  exsiccator 
Courtesy  of  Ekenberg  Co. 

of  wheat  flour.    It  is  then  ready  for  the  market,  which  it  reaches 
packed  in  either  tins,  boxes,  or  barrels. 

The  fact  that  the  milk  is  evaporated  under  reduced  pressure 
makes  it  possible  to  accomplish  the  drying  at  a  relatively  low 
temperature,  although  the  film  of  drying  milk  is  naturally  ex- 
posed for  a  very  brief  time  to  the  direct  heat  of  the  drum,  and 
which  obviously  varies  with  the  steam  pressure  in  the  drum. 
The  manufacturers  claim  that  the  drying  of  the  milk  takes  place 


MANUFACTURE  OF  MILK  POWDER 


287 


at  a  temperature  of  about  100  degrees  F.  and  that  the  milk  at 
no  time  reaches  temperatures  higher  than   120  degrees  F. 

The  Covers  Process. — This  process  and  equipment  was 
invented  and  patented  by  Francis  X.  Covers,  of  Owego,  New 
York,  U.  S.  patent  No.  939,495,  November  9,  1909. 

In  the  Covers  patent  the  milk  is  dried  on  two  revolving, 
hollow  cylinders  (5)  located  at  such  proximity  to  each  other 


Pig-.  97.     The  Govers  milk  drier 

that  there  is  practical  contact  at  the  periphery  of  the  two  cyl- 
inders, in  a  similar  manner  as  is  the  case  with  the  Just  process. 
These  revolving  cylinders,  however,  are  inclosed  and  operated 
in  an  outer  casing  which  serves  as  a  vacuum  chamber  (2),  which 
connects  with  a  vacuum  pump  through  pipe  (27).  There  is  a  milk 
supply  tank  (1)  with  regulating  valve  (4),  feeding  the  milk  to 
the  vacuum  chamber  through  pipe  (3).  Plates  (10)  which  bear 
against  the  opposite  ends  of  the  cylinders  (5)  form  with  the 
revolving  cylinders  a  receptacle  (13)  to  receive  and  retain  a 


288  MANUFACTURE  OF  MILK  POWDER 

small  quantity  of  the  milk  to  be  desiccated.  The  cylinders  are 
.charged  with  hot  water  through  pipes  (16).  Scrapers  (21)  re- 
move the  dried  milk  from  the  cylinders,  and  a  rotating  valve 
arrangement  (28  and  29)  is  provided  to  catch  the  dried  milk  as 
it  is  scraped  from  the  cylinders  and  to  carry  it  from  the  vacuum 
chamber  without  breaking  the  vacuum. 

In  the  operation  of  this  machine  it  is  aimed  to  maintain  a 
partial  vacuum,  sufficient  to  cause  the  milk  to  boil  at  a  ten> 
perature  of  about  157  degrees  F.  Through  the  revolving  metal 
cylinders  passes  a  continuous  flow  of  hot  water  at  a  temperature 
somewhat  higher  than  157  degrees  F.  but  below  212  degrees  F.. 
so  that  the  milk  is  never  exposed  to  212  degrees  F.  nor  over. 

In  the  small  receptacle  of  milk  at  (13)  to  which  the  milk 
is  continually  supplied  from  the  outside,  and  as  rapidly  as  it 
evaporates,  the  milk. is  heated,  to  about  157  degrees  F.  by  the 
revolving  cylinders.  It  is  partly  condensed  and  a  thin  film  of 
this  condensed  milk  coats  the  surface  of  the  cylinders  where  it 
dries,  the  dried  film  is  removed  from  the  cylinders  by  the  scrapers 
and  discharged  to  the  outside  of  the  apparatus  through  the  vanes 
of  the  four- winged  valves  (28),  located  near  the  bottom  on  both 
sides  of  the  vacuum  chamber. 

The  Buflovak  Process. — The  principle  of  drying  milk  and 
other  liquids  on  a  steam-  or  hot  water-heated  revolving  drum 
has  been  put  to  extensive  application  through  the  activities  of 
the  Buffalo  Foundry  &  Machine  Co.,  Buffalo,  N.  Y.  This  com- 
pany has,  during  the  last  decade,  invented,  constructed  and 
perfected  the  "Buflovak"  vacuum  drum  drier.  Patents  were 
granted  their  engineer,  Mr.  O.  S.  Sleeper,  by  the  United  States 
Government  in  1911,  1913,  1914,  1915  and  1916.  All  these  patents 
were  assigned  to  the  Buffalo  Foundry  &  Machine  Co. 

These  patents  pertain  to  the  drum  drier  as  used  for  whole 
milk,  skim  milk,  buttermilk  and  milk  products  in  general.  They 
are  applicable  to  other  products  as  well  as  to  milk,  but  for  milk 
they  are  made  specially  accessible  for  cleaning  and  for  sanitary 
control. 

The  Buflovak  drier  consists  of  a  casing  in  which  revolves 
a  steam-heated,  polished  drum.  The  milk  is  fed  to  the  surface 
or  periphery  of  this  drum  by  a  pan  located  beneath  the  drum 
and  placed  lightly  against  the  drum.  The  pan  has  an  overflow 


MANUFACTURE:  OF  MILK  POWDER 


289 


along  one  side  for  the  automatic  removal  of  the  surplus  milk  not 
taken  up  by  the  drum.  To  the  bottom  of  this  casing  is  supplied 
a  quantity  of  milk.  This  is  pumped  to  the  supply  pan  under  the 
drum,  the  overflowing  milk  running  back  into  the  lower  portion 


. 

Fig*.  98.     The  Buflovak  vacuum  drum  drier 
Courtesy  of  Buffalo  Foundry  &  Machine  Co. 

of  the  casing.  There  is  slight  pressure  in  the  supply  pan  which 
causes  the  drum  to  take  up  a  heavy  and  even  coating.  Near 
the  supply  pan  is  installed  a  leveling  arrangement  which  levels 
off  and  equalizes  the  layer  of  milk  on  the  drum.  As  the  drum 


290  MANUFACTURE  OF  MiivK  POWDER 

revolves  and  the  layer  of  milk  reaches  what  is  termed  the  front 
of  the  machine  it  is  continuously  removed  in  the  form  of  a  dry 
film  by  a  stationary  scraper.  At  this  point  the  machine  is  pro- 
vided with  a  breaker  which  consists  of  a  shaft  with  a  number 
of  rods  projecting  through  the  same,  which  revolves  to  break 
up  the  film  of  dried  milk  as  it  leaves  the  drum.  This  does  not 
reduce  the  film  to  a  powder,  but  causes  the  material  to  be  suffi- 
ciently broken  up  to  allow  it  to  fall  into  the  receiver  where  it 
can  be  easily  handled  for  removal. 

The  receiver  is  a  large  cylindrical  pan  placed  below  the 
scraper  at  the  front  of  the  machine.  Observation  glasses  are 
placed  so  that  all  internal  parts  may  be  seen  while  being  operated. 
The  receiver  is  equipped  at  each  end  with  a  door  of  the  full  width 
of  the  receiver,  facilitating  the  rapid  removal  of  the  dried  milk. 

Aside  from  the  circulating  pump  for  supplying  the  milk  to 
the  feed  pan,  there  is  a  condenser  and  a  dry  vacuum  pump.  Be- 
fore the  vapors  reach  the  condenser,  they  pass  through  a  dust 
collector.  This  is  water-sealed  and  prevents  the  accumulation 
in  the  vapor  pipe  of  any  dust  that  may  escape  from  the  drum 
and  pass  to  the  condenser. 

This  drier  is  operated  under  a  high  vacuum,  permitting  rapid 
evaporation  at  a  relatively  low  temperature.  The  actual  drying 
time  of  the  film  of  milk  on  the  drum  is  about  6  to  7  seconds. 
The  operation  is  continuous  and  at  the  conclusion  of  the  day's 
run  the  machine  is  washed  out.  If  subsequently  closed  up  and 
evacuated  for  a  few  minutes,  the  entire  interior  will  be  dry.  in- 
suring a  sanitary  condition  of  the  machine. 

3.    Spray-Drying  Processes. 

To  this  group  belong  the  several  processes  in  which  milk  is 
desiccated  by  atomizing  it  into  a  fine  spray  and  in  an  atmosphere 
or  current  of  heated  air.  The  small  particles  of  the  milk  spray  sur- 
render their  moisture  quickly  and  drop  to  the  bottom  of  the  drying 
chamber  in  the  form  of  flakes  of  dried  milk  while  the  moisture- 
laden  air  escapes  to  the  exterior,  screens  or  other  forms  of  dust  col- 
lectors being  provided  to  recover  such  parts  of  dried  milk  as  may 
escape  from  the  drying  chamber  with  the  expelled  air.  The  principle 
of  desiccating  fluid  substances  by  atomizing  them  into  an  atmosphere 


MANUFACTURE  OF  MILK  POWDER 


291 


,of  heated  air  dates  back  to  the  invention  of  Samuel  R.  Percy  in 
1872. 

The  Percy  Process. — This  process  was  invented  and  patented 
by  Samuel  R.  Percy  of  New  York  City,  U.  S.  patent  No.  125,406, 
April  9,  1872.  The  process  embraces  in  its  claims,  a  process  of 
atomizing  and  desiccating  fluid  and  solid  substances,  also  any  viscid 
substance  containing  water,  by  the  use  of  dried,  heated  or  cooled  air 
or  gas,  which  forces  the  substance  into  atoms ;  the  atoms  are  thrown 
forward,  and  forced  into  a  chamber  and  dried  in  consequence  of  the 
dried  or  heated  air  which  propels  them  into  the  chamber  and  also, 
owing  to  the  dried  and  heated  state  of  the  chamber  into  which  they 
are  thrown. 

The  Stauf  Process. — The  Stauf  process  represents  the  first 
commercially  successful  application  of  the  desiccation  of  milk  by 


rig-.  99.     The  Stauf  milk  drier 

the  spray-drying  principle  invented  by  Percy.  The  Stauf  process 
was  patented  by  Robert  Stauf  of  Posen,  Germany,  U.  S.  patent  No. 
666,711,  January  29,  1901. 

The  patent  claims  are  as  follows:     "The  process  of  obtaining 


292  MANUFACTURE  OF  MILK  POWDER 

the  solid  constituents  of  liquids,  such  as  blood,  milk  and  the  like,  in 
the  form  of  powder,  said  process  consisting  in  converting  the  liquid 
into  a  fine  spray,  bringing  such  spray  or  atomized  liquid  into  a  reg- 
ulated current  of  heated  air,  so  that  the  liquid  constituents  are  com- 
pletely vaporized,  conveying  the  dry  powder  into  a  suitable  collect- 
ing space  away  from  the  air  current,  and  discharging  the  air  and 
vapor  separately  from  the  dry  powder." 

The  Stauf  patent  shows  a  vertical  drying  chamber  (e)  into 
which  the  liquid  (milk)  to  be  desiccated  is  atomized  through  jets 
or  nozzles  (b)  under  pressure,  into  a  fine  spray.  A  current  of 
heated  air  is  admitted  at  the  bottom  of  the  drying  chamber  (f )  run- 
ning in  the  same  direction  as,  and  mixing  with,  the  spray  of  milk, 
and  evaporating  the  watery  constituents  of  the  spray.  The  steam 
and  dried  particles  are  carried  upward  by  the  heated  air,  retaining 
the  atoms  momentarily  in  the  current  of  hot  air  and  causing  them 
to  surrender  substantially  all  the  remaining  moisture  in  the  form  of 
vapor,  and  the  product  is  prevented  by  the  cooling  effect  of  such 
evaporation  from  undergoing  chemical  change.  The  vapors  and 
dried  atoms  are  guided  by  a  cone  (g)  extending  downward  from  the 
top  into  the  drying  chamber,  into  collecting  chambers  (h)  where  the 
desiccated  milk  or  dry  powder  gathers  in  hoppers  (i)  away  from 
the  vaporizing  current.  The  moisture-laden  air  or  gas  is  separated 
from  the  dry  powder  and  escapes  through  the  sides  of  the  collecting 
chamber,  which  consist  of  mill  gauze,  woolen  fabric  or  like  pervious 
material. 

The  McLachlan  Process. — This  process  was  patented  by 
John  C.  McLachlan  of  Chicago,  111.,  U.  S.  patent  No.  806,747,  De- 
cember 5,  1905.  This  process  is  a  modification  of  the  Stauf  process. 

McLachlan  uses  a  tall  vertical  drying  chamber  (B)  surrounded 
on  its  sides  by  a  jacket  or  casing  (A),  containing  steam  heating  coils 
(G)  with  intake,  and  outlet  of  steam;  a  circular,  perforated  pipe 
(M)  is  installed  near  the  top  of  the  chamber  for  the  purpose  of  dis- 
charging into  the  chamber  heated  air,  an  atomizing  jet  (O5)  enters 
through  the  side  of  the  drying  chamber  near  the  top,  an  air  pump 
(O)  forcing  heated  air  into  the  atomizing  nozzle  (O5),  a  slide  door 
(D)  at  the  bottom  of  the  drying  chamber  for  the  discharge  of  the 
dried  powder  through  opening  (E),  and  a  perforated  covering  (K) 
over  the  top  of  the  drying  chamber  for  the  escape  of  the  moisture- 
laden  air. 


MANUFACTURE:  OF  MILK  POWDER 


293 


In  this  apparatus  the  spray  of  the  milk  enters  into  the  upper 
part  of  the  drying  chamber  and  is  permitted  to  drop  through  an 
atmosphere  of  heated  air.  As  the  atoms  of  drying  milk  descend, 
they  surrender  more  and  more  of  their  moisture  and  at  a  certain  point 
toward  the  bottom  they  have  discharged  substantially  all  their  mois- 


j~ 


03 


_\ 

Lk_ 

Sll 

Tig.  100.     The  McLachlan  milk  drier 

ture  and  are  deposited  in  the  form  of  a  dry  powder  in  the  bottom 
of  the  drying  chamber,  from  where  they  are  discharged  by  a  slide 
door.  In  the  meantime  the  vapors  pass  freely  up  and  out  of  the 
upper  or  open  end  of  the  chamber. 

This  process  differs  from  the  Stauf  process  essentially  only  in 
the  fact  that  the  milk  descends  through  an  atmosphere  of  heated  air 
and  that  the  drying  chamber  and  the  collecting  chamber  are  one  and 


294  MANUFACTURE  OF  MILK  POWDER 

the  same,  while  in  the  Stauf  patent  the  milk  spray  ascends  and  is 
carried  into  separate  collecting  chambers. 

In  a  later  design,  U.  S.  patent  No.  1,038,773,  September  17, 
1912,  McLachlan  causes  the  heated  air  to  be  forced  into  the  drying 
chamber  through  a  rotating  discharge  head  located  in  the  center  of 
the  drying  chamber.  The  rotating  discharge  head  directs  the  air 
currents  radially  outward  toward  a  deflecting  ring. 

The  milk  is  blown  into  the  drying  chamber  through  multiple 
supply  nozzles  or  atomizers.  These  supply  nozzles  enter  through  the 
periphery  of  the  deflecting  ring.  They  discharge  in  a  horizontal 
plane  and  incline  to  the  radius  in  such  a  manner  as  to  cause  maxi- 
mum commingling  of  the  finely  divided  particles  of  the  milk  with  the 
heated  air.  The  dried  powder,  deposits  in  the  bottom  of  the  drying 
chamber,  a  belt  conveyor  discharges  it  into  a  screw  conveyor  pocket, 
whence  it  is  removed  to  any  suitable  storage  container. 

The  moisture-laden  air  leaves  the  drying  chamber  through 
drums  near  the  bottom  and  top  of  the  drying  chamber.  These  dis- 
charge drums  are  equipped  with  suitable  arrangement  to  recover 
such  parts  of  the  powder  as  are  deposited  on  their  surfaces. 

The  Merrell-Merrell-Gere  Process. — This  process  is  similar 
to  the  Stauf  process  except  that  the  patent  covering  the  Merrell- 
Merrell-Gere  process  specifically  refers  to  the  desiccation  of  pre- 
viously condensed  milk,  while  the  Stauf  patent  makes  no  specific  ref- 
erence to  the  use  of  condensed  milk,  although  the  term  "milk"  may 
have  been  intended  to  embrace  all  kinds  of  milk  regardless  of  the 
degree  of  concentration  prior  to  desiccation. 

The  Merrell-Soule  Co.,  of  Syracuse,  N.  Y.,  purchased  the 
Stauf  patent  in  1905  and  two  years  later  L.  C.  Merrell,  I.  S.  Merrell 
and  W.  B.  Gere,  of  Syracuse,  N.  Y.,  assignors  to  Merrell-Soule  Co. 
patented  the  process  as  applied  to  desiccating  condensed  milk,  U.  S. 
patent  No.  860,929,  July  23,  1907.  Their  patent  claims  read  as 
follows :' 

1.  "The  process  of  obtaining  the  solid  constituents  of 
liquids  and  semi-liquids,  in  the  form  of  powder,  which  process 
consists  in  concentrating  the  substance  by  removing"  a  large 
percentage  of  the  water  therefrom,  converting-  the  concentrated 
mass  into  a  fine  spray,  bringing  such  spray  into  a  current  of  dry 
air  or  gas  having  an  avidity  for  moisture  so  that  substantially 
all  the  remaining  liquid  constituents  are  separated  thereby, 


MANUFACTURE  OF  MILK  POWDER 


295 


conveying  the  dry  powder  into  a  suitable  collecting  space  away 
from  the  air  or  gas  current,  and  discharging  th-e  air  or  gas  sepa- 
rately from  the  dry  powder. 

2.  "The  process  of  obtaining  the  solid  constituents  of  liquids 
and  semi-liquids,  in  the  form  of  powder,  which  process  consists 
in  concentrating  the  substance  by  removing  a  large  percentage 
of  water  therefrom,  converting  the  concentrated  mass  into  a 
spray,  bringing  such  spray  into  a  current  of  dry  heated  air  or 
gas  having  an  avidity  for  the  moisture  of  the  substance  treated, 
retaining  the  atoms  momentarily  in  said  current  so  that  sub- 
stantially all  the  remaining  moisture  is  converted  into  vapor 


Fig-.   101.     The  Merrell-Soule   milk   drier 


and  the  product  is  prevented  by  the  cooling  effect  of  such  evap- 
oration from  undergoing  chemical  change,  conveying  the  dry 
powder  into  a  suitable  collecting  space  away  from  the  vaporizing 
current,  and  discharging  the  air  or  gas  separately  from  the  dry 
powder." 

The  Merrell-Soule  Co.  are  operating  numerous  powdered 
milk  factories,  with  headquarters  in  Syracuse,  N.  Y.  This  com- 
pany has  subjected  the  spray-drying  process  to  much  experi- 
mental study  in  efforts  to  perfect  the  process  and  to  improve 
the  quality  and  keeping  properties  of  the  product. 

Obviously,  during  the  life  of  the  Stauf  patent,  which  ex- 
pired January  29,  1918,  no  one  could  make  milk  powder  by  the 
spray-drying  process,  whether  from  milk  uncondensed,  or  from 


1  From  Plaintiff's  Record  in   the  U.   S.   District  Court. 
v{3.  Rico  Milk  Products  Co. 


Merrell-Soule  Co. 


296 


MANUFACTURE  OF  MILK  POWDER 


milk  previously  condensed  without  paying  tribute  to  the  owners 
oi  this  patent,  the  Merrell-Soule  Co. 

The  C.  E.  Rogers  Process. — This  process  was  patented  by 
Charles  E.  Rogers  of  Detroit,  Mich.,  U.  S.  patent  No.  1,226,001, 
Mav  15,  1917,  and  No.  1,243,878,  October  23,  1917. 


Tig.  102  and  Pig".  103.     Rogers  milk  drier 

Courtesy  of  C.  E.  Rogers 


1  desiccating  chamber,  2  spray  nozzles,  3  spray  pipes,  4  hot  air  inlet  con- 
duit, e  end  of  air  conduit,  °  deflector,  7  air  discharge  conduits,  8  recovery 
screens,  9  pivots,  10  bar,  "  loose  screens  for  vibrating,  12  springs,  13  rods  con- 
tacting- with  14  cams. 

The  patent  claims  cover  the  desiccation  by  the  spray-drying 
process  of  fluids  including  condensed  milk.  The  apparatus  con- 
sists of  a  large  drying  chamber,  the  spray  nozzles  are  located 
near  the  top  on  all  four  sides  of  the  chamber.  The  hot  air  is 


MANUFACTURE  OF  MILK  POWDER  297 

admitted  near  the  bottom  in  the  center  of  the  drying  chamber, 
means  for  heating  the  air,  blowing  it  into  the  drying  chamber 
and  screens  located  near  the  bottom  at  the  periphery  of  the 
chamber  for  discharging  the  spent  air  are  provided. 

In  this  apparatus  the  sprayed  milk  falls  from  near  the  top 
of  the  drying  chamber  through  an  ascending  current  of  heated 
air.  The  milk  spray  entering  on  all  sides  causes  an  even  distribu- 
tion of  the  spray  particles  and  a  consequent  even  deposit  of  the 
dried  milk  particles  on  the  bottom  of  the  drying  chamber.  The 
previously  condensed  milk  is  sprayed  into  the  drying  chamber 
while  heated  to  a  temperature  of  140  degrees  F.,  the  temperature 
of  the  air  in  the  drying  chamber  ranges  from  180  to  200  degrees 
F.  The  distance  over  which  the  spray  falls  through  the  ascend- 
ing current  of  heated  air  being  sufficient  to  permit  the  removal 
from  .the  milk  particles  of  substantially  all  the  remaining 
moisture. 

The  Gray  Process. — Chester  Earl  Gray  of  Eureka,  Calif., 
and  Aage  Jensen  of  Oakland,  Calif..  U.  S.  patent  No.  1,078,848, 
November  18,  1913,  Chester  Earl  Gray,  Assignor  of  one-half  to 
Aage  Jensen,  U.  S.  patent  No.  1,107,784,  August  18,  1914,  and 
Chester  Earl  Gray,  U.  S.  patent  No.  1,157,935,  October  26,  1915, 
and  U.  S.  patent  No.  1,266,013,  May  14,  1918,  subjected  the  pos- 
sibilities of  spray  drying  to  extensive  study  and  invented  and 
patented  successive  improvements  and  new  principles  relating 
to  desiccation  of  milk  and  other  liquid  substances. 

Gray  patent  No.  1,107,784  involves  an  apparatus  with  a 
circular  desiccating  chamber  A,  having  a  cone-shape  lower  sec- 
tion B,  terminating  in  a  discharge  opening  for  the  dried  sub- 
stance, and  a  discharge  opening  C  for  the  moisture-laden  air. 
The  heated  air  is  introduced  into  the  desiccating  chamber 
peripherally  in  a  tangential  direction,  by  means  of  a  blower  D. 
Between  the  blower  and  the  drying  chamber  there  is  an  inclosed 
heating  coil  (steam  coil)  over  and  around  which  the  air  is  blown 
into  the  drying  chamber.  The  tangential  entry  of  the  heated  air 
into  the  circular  chamber  sets  up  a  cyclonic  current  therein  and 
this  effect  is  augmented  by  introducing  the  air  at  several  different 
points  through  tangential  openings  a.  The  milk  to  be  desiccated 
enters  under  pressure  through  a-  spray  nozzle  H,  located  in  the 


298 


MANUFACTURE  OF  MILK  POWDER 


center  of  the  chamber  and  is  atomized.     The  distinctive  features 
of  this  process  are : 

1.  The  heated  air  enters  at  the  periphery,  forms  a  cyclonic 
current  moving  tangentially  toward  the  center  where  the  moisture- 
laden  air  escapes  at  C. 

2.  The  atomized  milk  enters  at  the  center  of  the  cyclonic 
air  current,  partakes  of  the  rotary  movement  of  the  air  current, 
but  because  of  their  greater  specific  gravity  the  particles  of  dry- 
ing milk  influenced  by  centrifugal  force  are  caused  to  travel  in 


Tig.  104.     The  Gray  milk  drier 

spiral  lines  outwardly  through  the  current  of  air  and  are  finally 
arrested  by  the  confining  walls  of  the  chamber  dowft  which 
they  fall  to  the  discharge  end  at  the  bottom. 

3.  The  exhaustiveness  of  the  removal  of  moisture  from  the 
particles  of  milk  is  augmented  by  the  fact  that  the  heated  air 
moving  through  the  spray  of  milk  spirally  toward  the  center, 
where  it  escapes,  has  taken  up  its  maximum  charge  of  moisture 
by  the  time  it  reaches  the  center,  which  is  the  point  of  its  dis- 
charge and  it  is  dryest  near  the  periphery.  The  spray  of  milk 


MANUFACTURE:  OF  MILK  POWDER  299 

being  discharged  into  the  cyclonic  current  at  the  center,  carries 
its  maximum  moisture  content  at  that  point,  gradually  surrenders 
it  to  the  air,  as  it  moves  outwiard  to  the  periphery  of  the  cyclonic 
current.  The  completion  of  the  drying  is  accomplished  in  the 
zones  of  incoming  heated  air  which  carry  the  least  humidity. 
Therefore,  as  the  outwardly  moving  particles  of  milk  surrender 
more  and  more  of  their  moisture,  they  pass  through  dryer  zones 
of  heated  air.  This  obviously  both  accelerates  the  speed  of 
drying  and  enhances  the  completeness  of  the  removal  of  moisture. 

4.  Inasmuch  as  trie  danger  of  the  solubility-destroying  effect 
of  heat  is  greatest  while  the  milk  is  still  in  the  liquid  state,  and 
this  effect  is  practically  completely  absent  in  milk  from   which 
the  bulk  of  moisture  has  been  removed,  this  process  has  the  ad- 
ditional  advantage  of  maximum   preservation   of  the   solubility 
in   the   finished   product.     The   temperature   of  the   cyclonic   air 
current  is  lowest  when  it  reaches  the  center  where  the  moisture 
content  of  the  milk  is  greatest.    By  the  time  the  particles  of  milk 
come  in   contact  with   the  hottest  air    (at  the  periphery)    their 
moisture  content  is  lowest. 

5.  This   process  tends   to   facilitate   maximum   recovery   of 
the  milk  powder.     The  moisture-laden  air  escapes  in  the  center, 
where  the  particles  of  milk  are  heaviest,  and  where  their  greater 
specific  gravity  causes  them  to  partake  of  the  centrifugal  motion 
moving  them  outward  until  when  completely  dried,  they  strike 
the  steeply  tapered  confining  walls  of  the  drying  chamber  and 
fall  to  the  bottom  of  this  chamber. 

Gray  patent  No.  1,157,935  involves,  in  addition  to  the  new 
and  advantageous  features  established  under  patent  No.  1,107,784. 
and  explained  above,  apparatus  and  a  method  for  supporting  the 
milk  or  other  substance  to  be  desiccated  on  and  by  the  introduc- 
tion of  a  solid,  sheet-like,  or  finely  divided  substance.  In  the 
case  of  milk,  the  supporting  or  absorbing  material  used  may  be 
previously  desiccated  milk. 

The  desiccating  chamber  A  described  in  this  patent  is  similar 
to  the  desiccating  chamber  shown  under  patent  No.  1,107,784. 
and  the  intake  of  the  heated  air  B  and  discharge  of  the  moisture- 
laden  air  C  are  unchanged.  The  intake  of  the  milk  and  support- 
ing material  into  the  desiccating  chamber  is  located  in  the  center 


300 


MANUFACTURE;  OF  MILK  POWDKR 


near  the  top  of  this  chamber.    The  milk  and  supporting  material 
enter  through  an  inlet  duct  E,  through  which  a  shaft  F  extends 


]  1JB,J  1 


Pig-.  105.     Tlie  Gray  milk  drier 

down  to  a  vaned  distributer  G,  which  is  revolved  by  any  suitable 
power  mechanism.     The  material  to  be  dried  enters  the  duct  E 


MANUFACTURE  OF  MILK  POWDER  301 

at  the  upper  end  being  fed  thereto  by  a  screw  conveyor  H,  which 
receives  the  product  from  the  coating  chamber  I  which  is  located 
above  the  drying  chamber.  The  coating  chamber  is  cone  shape. 
At  the  upper  end  of  this  chamber  there  is  provided  a  means  for 
introducing  the  nucleus  mass  or  supporting  material,  in  this  case 
the  previously  desiccated  milk,  and  distributing  the  same  in  the 
chamber,  as  well  as  a  means  for  maintaining  in  this  chamber  an 
atmosphere  which  carries  the  milk  to  be  desiccated  in  com- 
minuted form.  The  nucleus  mass  or  supporting  material  is  fed 
to  a  rotary  distributer  K  by  a  screw  conveyor  M,  receiving  its 
material  from  a  hopper  N.  Extending  down  through  a  hollow 
shaft  L  is  a  pipe  O  terminating  in  an  atomizing  nozzle  and  the 
milk  to  be  desiccated  is  forced  through  the  pipe  and  nozzle  under 
pressure.  By  this  arrangement  the  comminuted  milk  and  the 
comminuted  supporting  material  come  into  intimate  contact 
whereby  the  particles  of  the  supporting  material  become  coated 
with  the  milk  to  be  desiccated. 

At  the  bottom  of  the  desiccating  chamber  a  grading  mechan- 
ism is  provided  consisting  of  shaking  screens  Q  and  O1  and  a 
hopper  P  which  separate  the  desiccated  milk  into  three  grades. 
Shaking  screen  Q  is  of  relatively  large  mesh.  It  is  designed  to 
remove  only  the  larger  particles  which  pass  from  this  screen  to 
a  pulverizing  apparatus  R  where  they  are  reduced  to  a  finer 
condition.  The  material  passing  through  screen  Q  drops  on 
screen  Q1,  the  mesh  of  which  is  of  such  size  as  to  permit  the 
passage  of  only  the  finer  particles,  while  the  intermediate  sized 
particles  are  discharged  into  receptacle  S  as  the  finished  product. 
The  finer  particles  pass  down  onto  a  shaking  floor  Q2  and  from 
there  into  a  receiver  U,  which  may  also  receive  the  pulverized 
material  from  pulverizer  R.  A  conveyor  V  carries  the  material 
from  receiver  U  up  into  hopper  N,  this  material  constituting  the 
nucleus  mass  or  supporting  material  used  for  desiccating  the  milk. 
There  is  no  drying  action  in  the  coating  chamber. 

This  apparatus  and  process  may  be  operated  continuously 
and  after  it  is  once  in  operation  the  output  is  claimed  to  be  equal 
to  or  greater  than  Would  be  possible,  with  an  apparatus  in  which 
the  liquid  milk  itself  is  sprayed  into  the  current  of  heated  air. 

This  process  yields  a  product  having  particles  of  appreciable 
size,  which  facilitates  ease  and  completeness  of  solution  in  water. 


302 


MANUFACTURE  OF  MILK  POWDER 


It  is  superior  in  this  respect  to  the  fine  state  of  division  of  the 
product  of  other  processes,  in  which  state  the  particles  are  more 
difficult  of  mixture  and  solution,  though  they  may  be  equally 
soluble. 

Gray  patent  No.  1,266,013  deviates  in  principle  from  No. 
1,157,935,  in  that  the  liquid  to  be  desiccated  is  distributed  on  a 
desiccating  supporting  surface,  and  the  dried  milk  is  removed 
from  this  surface  in  finely  divided  form.  The  operation  is  made 
continuous  by  causing  the  spraying  or  depositing  devices  to 
travel  in  unison  with  the  devices  for  removing  the  dried  material, 
but  so  as  to  deposit  the  liquid  on  the  supporting  surface  after  the 
same  has  been  cleaned  of  the  dried  substance. 

The  d  e  s  i  c  c  ating 
chamber  is  of  large 
size  and  cone-shape. 
The  inclined  or  taper- 
ing sides  A  form  the 
supporting  surface.  It 
terminates  at  its  bot- 
tom in  a  suitable  dis- 
charge opening  B,  reg- 
ulated by  a  valve  b.  At 
the  top  in  the  center 
there  is  an  exit  C  for 
the  moisture-laden  air, 
and  peripheral  inlet 
openings  D  for  the 
heated  air,  similar  as  in 
the  apparatus  of  the 
two  previous  patents, 
and  so  arranged  as  to 
create  in  the  drying 
chamber  a  cyclonic 
action,  whereby  any 
particles  heavier  than  «*  106'  ^e  Gray  milk  drier 

the  air  are  caused  to  seek  the  walls  of  the  chamber  and  be 
deposited  thereon.  In  the  center  of  the  upper  portion  of  the 
drying  chamber  is  a  rotary  spray  nozzle  F,  arranged  to  direct 
the  milk  in  a  fan-shaped  spray  against  the  inclined  wall  A.  The 


THE  SPRAY  PROCESS  303 

milk  reaches  the  spray  nozzle  under  pressure  through  pipe  G. 
The  nozzle  rotates  by  means  of  a  traveler  I  supported  by  a  track 
i  and  a  roller  arrangement  i1.  The  traveler  extends  down  through 
the  desiccating  chamber,  with  driving  attachment  K  and  L  near 
bottom.  The  traveler  is  provided  with  a  brush  made  of  a  mass 
of  chain  links  M,  depending  from  the  traveler  and  resting  in 
contact  with  the  inner  surface  of  the  inclined  wall  A.  This  brush 
insures  the  removal  of  the  dried  material  from  the  surface  in 
finely  divided  form. 

If  it  is  desired  to  control  the  temperature  of  the  supporting 
surface  A  during  the  drying  operation,  the  supporting  wall  may 
be  jacketed,  thereby  forming  a  surrounding  chamber  N  through 
which  a  circulating  medium  of  the  desired  temperature  may  be 
passed  to  effect  the  proper  control  of  the  temperature  of  the 
surface. 

The  design  and  arrangement  of  the  apparatus  covered  by 
the  above  patent  is  such  that  while  the  major  portion  of  the 
surface  is  constantly  exposed  to  the  drying  effect  of  the  cyclonic 
current  *of  the  heated  air,  the  brush  and  the  traveler  which 
propels  it,  advance  around  the  chamber  so  as  to  remove  the 
dried  milk  from  each  portion  of  the  surface  in  succession  and  the 
spray  nozzle  operates  in  such  a  manner  as  to  direct  the  spray 
of  milk  against  the  surface  in  the  rear  of  the  traveler  and  brush, 
or  on  that  portion  of  the  surface  from  which  the  dried  milk  has 
been  removed.1 

CHAPTER  XXVI. 

COMMERCIAL  MANUFACTURE  OF  MILK  POWDER  BY 
THE  SPRAY  PROCESS. 

Pre-heating  of  Milk. — It  has  been  demontrated  that  in  order 
to  preserve  maximum  solubility  of  the  finished  product,  the  fluid 
milk  should  not  be  heated  above  150  degrees  F. 

Accordingly  the  practice  has  been  generally  adopted  in 
'plants  drying  milk  by  spray-drying  to  heat  the  milk  to  from 
140  to  150  degrees  F.  For  this  purpose  similar  equipment  is 
used  as  in  the  manufacture  of  condensed  milk. 

Pre-condensing  of  Milk. — While,  in  the  early  days  of  the 
use  of  the  spray-drying  principle  for  desiccating  milk,  the  fluid 


]  See  also  Dick  process,  page  335. 


304  THE  SPRAY  PROCESS 

milk,  without  precondensing,  was  sprayed,  and  while  this  pro- 
cedure is  entirely  feasible,  it  was  soon  found  that  it  was  more 
economical  to  remove  a  considerable  portion  of  the  water  of  the 
fluid  milk  and  to  reduce  the  product  to  a  concentration  of  about 
4:1  or  4.5:1  before  spraying.  This  is  accomplished  by  condens- 
ing the  fluid  milk  by  any  of  the  methods  for  condensing  as  de- 
scribed under  the  "Manufacture  of  Condensed  Milk"  in  this 
volume.  In  general  practice  the  vacuum  pan  is  used  for  this 
purpose  in  most  of  the  milk  powder  plants. 

Effect  of  Pre-condensing  on  Economy  of  Manufacture. — 
The  chief  advantage  and  purpose  of  pre-condensing,  instead 
of  spraying  the  fluid,  or  uncondensed  milk,  lies  in  the  greater 
economy  of  operation  in  the  case  of  pre-condensing. 

The  fluid  milk  contains  more  water  than  the  condensed 
milk;  more  water  must  be  removed  during  the  spraying  process, 
hence  less  milk  can  be  desiccated  in  equipment  of  the  same  capa- 
city and  in  the  same  space  of  time  than  in  the  case  of  spraying 
pre-condensed  milk.  The  pre-condensing  therefore  means  greater 
capacity  of  the  available  equipment-  shorter  hours  and  greater 
economy  of  operation. 

Again,  the  fuel  requirements  are  greater  in  the  process  of 
desiccating  by  the  spray  method  than  by  evaporation  in  the 
vacuum  pan  or  the  film  method.  The  comparative  efficiency 
of  evaporating  water  by  means  of  air  and  in  vacuum,  is  well 
understood.  The  heat-transmitting  coefficient  of  air  is  much 
lower  than  that  of  steam  and  metal  heating  surfaces.  The 
heat  applied  in  the  form  of  heated  air  is  less  completely  utilized 
than  the  heat  applied  in  the  form  of  steam  in  copper  jackets  and 
coils,  hence  in  evaporation  by  heated  air  there  is  greater  waste 
of  heat  and  fuel.  The  various  factors  which  enter  into  the  dry- 
ing by  means  of  air  and  the  resulting  losses  of  heat  transferred 
are  discussed  in  detail  by  E.  Hausbrand1  in  his  revised  treatise 
entitled  "Drying  by  Means  of  Air  and  Steam." 

Effect  of  Pre-condensing  on  Bulkiness  of  Spray  Milk 
Powder. — Other  conditions,  such  as  orifice  of  spray  nozzle, 
pressure  of  milk,  and  temperature  to  which  the  milk  is  preheated 
being  the  same,  the  milk  powder  made  by  spraying  fluid  or  un- 
condensed milk,  is  somewhat  more  bulky  than  that  made  by 


1  Hausbrand.     "Drying  by  Means  of  Air  and  Steam,"   1901. 


THE:  SPRAY  PROCESS  305 

pre-condensing  the  milk  before  spraying".  The  spraying  of  tin- 
condensed  milk  appears  to  produce  a  more  flaky  powder  while 
the  spraying  of  condensed  milk  results  in  a  more  granular 
powder.  The  flake  shape  does  not  pack  as  closely  together  as 
the  granular  shape.  This  is  obviously  an  advantage  in  favor  of 
{ire-condensing. 

However,  the  physical  shape  and  condition  of  the  powdered 
milk  can  be  controlled  to  a  considerable  extent  by  modification 
of  the  coarseness  or  fineness  of  the  spray.  In  fact,  by  such  modi- 
fication it  is  possible  to  make  a  distinctly  granular  product  from 
uncondensed  milk,  and  a  decidedly  flaky  product  from  the  pre- 
condensed  milk. 

The  finer  the  spray  the  more  flaky  the  milk  powder;  the 
coarser  the  spray  the  more  granular  the  milk  powder.  The  fluid 
milk  makes  a  finer  spray  than  the  condensed  milk;  therefore  the 
more  flaky  condition  of  the  powder  from  the  former. 

Aside  from  the  concentration  of  the  milk  to  be  sprayed,  the 
fineness  or  coarseness  of  the  spray  can  be  regulated  by  the  size 
of  the  orifice  of  the  spray  nozzles  and  by  the  pressure  of  the 
milk.  The  larger  the  orifice  or  the  lowier  the  pressure,  or  both, 
the  coarser  will  be  the  spray  and  consequently  the 'more  granular 
the  milk  powder.  Therefore,  in  order  to  reduce  the  flakiness 
and  bulkiness  of  milk  powder  made  from  uncondensed  milk,  and 
to  make  this  milk  powder  more  granular,  the  orifices  of  the 
spray  nozzles  must  be  relatively  large  or  the  pressure  of  the 
milk  must  be  relatively  low,  or  both.  Superheating  of  the  milk 
(boiling  it  at  212  degrees  F.)  by  turning  steam  direct  into  it 
also  assists  in  minimizing  the  fluffiness  and  bulkiness  of  the  re- 
sulting milk  powder  but  it  diminishes  the  solubility  of  the 
product. 

Effect  of  Pre-condensing  on  Keeping  Quality  of  Spray  Milk 
Powder. — Inasmuch  as  the  spray  milk  powder  that  is  now  com- 
mercially manufactured  does  not  contain  enough  moisture, 
when  properly  desiccated  and  protected  from  dampness,  to 
sustain  bacterial  action,  the  keeping  quality  of  this  product  does 
not  materially  depend  on  bacterial  decomposition  or  freedom 
therefrom. 

Milk  powder  does  became  stale  with  age,  however,  and 
much  of  it  gradually  develops  a  tallowy  flavor  and  odor.  This 


306  THE  SPRAY  PROCESS 

must  be  attributed  to  chemical  changes,  one  of  the  chief  of  which 
is  oxidation.  While  there  are  numerous  agents,  which  come  in 
contact  with,  or  enter  into,  the  composition  of  milk  powder,  that 
may  bring  about,  or  may  invite  oxidation,  air  is  one  of  the  most 
likely  factors  to  play  an  important  role. 

Air,  as  is  well  known,  acts  as  an  oxidizing  agent.  Since 
there  is  a  noticeable  tendency  of  the  product  from  uncondensed 
milk  to  be  flakier  and  bulkier  than  the  product  from  condensed 
milk,  it  appears  that  with  this  increased  bulkiness,  there  may 
be  more  air  in  a  given  bulk,  varying  somewhat  with  the  method 
of  packing. 

But  experience  has  shown  that  there  is  enough  air  contained 
both,  in  a  package  of  milk  powder  made  from  uncondensed  milk 
and  in  a  like  package  of  milk  powder  made  from  condensed 
milk,  to  cause  deterioration,  when  other  conditions,  such  as 
light,  or  temperature,  or  both,  are  favorable,  or  when  there  is 
present  in  the  product  enough  moisture. 

There  are  no  experimental  results  available  that  show  any 
difference  in  the  keeping  quality  of  the  two  products  and  the 
experience  of  the  commercial  manufacturer  points  to  the  con- 
clusion that  the  milk  powder  made  from  uncondensed  milk 
keeps  as  well  as  the  product  made  from  pre-condensed  milk. 

Effect  of  Pre-condensing  on  Solubility  of  the  Spray  Milk 
Powder. — The  flaky  and  fluffy  powder  of  the  uncondensed  milk 
goes  into  solution  at  the  start  somewhat  slower  than  the  more 
granular  powder  made  of  condensed  milk.  This  is  due  to  the 
fact  that  the  flaky  particles  with  their  relatively  large  exposed 
surfaces,  coming  in  immediate  contact  with  the  water,  dissolve 
and  take  up  water  so  rapidly,  that  they  run  together  and  paste, 
forming  a  coating  around  the  remaining  mass  of  the  product, 
which  renders  the  penetration  of  the  water  into  the  mass  some- 
what slower  at  the  start.  However,  this  is  no  indication  that 
the  flaky  powder  is  less  soluble  than  the  granular  powder,  in 
fact  the  flaky  powder,  because  of  the  large  relative  surfaces  of 
its  particles  and,  therefore,  the  greater  area  of  contact,  does 
dissolve  more  rapidly  when  it  actually  comes  in  contact  with 
water. 

Experiments  conducted  by  Hunziker  indicate  that  the  differ- 
ence in  speed  of  solution  between  the  two  products  is  very  slight 


THE  SPRAY  PROCESS  307 

and  that  the  total  solubility  is  very  slightly  greater  in  the  case 
of  the  more  flaky  milk  powder  made  from  uncondensed  milk. 
In  these  experiments  the  amount  of  milk  powder,  the  amount 
and  temperature  of  the  water  and  the  kind  and  amount  of  me- 
chanical agitation  were  exactly  alike.  At  the  end  of  one  minute 
from  the  time  the  milk  powders  were  put  into  the  water,  the 
amount  of  solids  dissolved  was  practically  the  same  in  the  case 
of  the  flaky  powder  made  from  uncondensed  milk  as  it  was  in 
the  case  of  the  granular  powder  made  from  pre-condensed  milk. 
And  after  that  the  percentage  of  total  solids  dissolved  from  the 
powder  made  from  uncondensed  milk  was  slightly  greater  than 
the  percentage  of  total  solids  dissolved  at  the  end  of  the  same 
respective  periods  of  time  from  the  powder  made  from  pre-con- 
densed milk. 

Here  again  it  should  be  understood  that  uncondensed  milk 
may  be  so  atomized  and  dried  (large  orifice  of  spray  nozzle  and 
low  pressure)  to  increase  the  size  and  granular  condition  of 
the  particles  of  the  resulting  powder  sufficiently,  so  that  for 
all  purposes  for  which  milk  powders  are  used  commercially  and 
domestically  the  ease  or  difficulty  of  solution  is  no  longer  any 
factor. 

Effect  of  Pre-condensing  on  Recovery  of  Spray  Milk  Powder. 
—The  finer,  lighter  and  more  fluffy  the  milk  powder  the  greater 
is  the  tendency  of  a  portion  of  the  powder  to  escape  from  the 
drying  chamber.  Hence  it  is  obvious  that  the  product  from  un- 
condensed milk,  when  desiccated  in  such  a  manner  as  to  intensify 
the  flakiness  at  the  expense  of  a  granular  condition  (small  orifice 
of  spray  nozzle  and  high  pressure),  will  tend  to  escape  from 
the  drying  chamber  more  profusely  than  the  more  granular 
powder  made  from  pre-condensed  milk.  Pre-condensing  facil- 
itates maximum  recovery. 

It  should  be  borne  in  mind,  however,  that  the  fineness  of 
some  of  the  particles  of  dried  milk  made  from  either  uncon- 
densed or  pre-condensed  milk,  makes  necessary  the  use  of  an 
efficient  dust  collector.  Without  such  a  dust  collector,  a  portion 
of  the  finer  and  lighter  particles  will  be  lost  in  either  case.  In 
the  case  of  the  flakier  and  finer  product  of  uncondensed  milk, 
the  dust  collector  must  be  such  as  to  collect  a  product  of  that 


308  THE:  SPRAY  PROCESS 

fineness,   in  order   to   be   efficient  and   to  accomplish   maximum 
recovery. 

The  percentage  of  recovery  of  the  solids  of  milk  in  the  form 
of  milk  powder  in  any  given  desiccating  arrangement  then  is 
largely  a  matter  of  efficiency  of  the  dust  collector,  and  the  effi- 
ciency of  dust  collectors  must  increase  as  the  fineness  and  flaki- 
ness  of  the  product  increases.  The  recovery  may  be  materially 
facilitated,  however,  by  such  an  arrangement  of  the  desiccating 
apparatus,  as  will  cause  the  particles  of  drying  milk  to  travel 
in  a  direction  opposite  to  that  of  the  escaping  air,  as  indicated 
in  the  Gray  patents. 

Heating  the  Air. — This  is  done  either  by  the  installation 
and  operation  of  a  furnace,  similar  in  principle  to  hot  air  fur- 
naces, or  by  steam  coils  installed  in  a  closed,  insulated  vault. 

The  hot  air  furnace  makes  possible  the  heating  of  the  air 
to  higher  temperatures  and  it  is  claimed  to  be  somewhat  more 
economical  from  the  standpoint  of  fuel  consumption.  Its  dis- 
advantages are  that  the  temperature  is  somewhat  more  difficult 
to  control,  it  fluctuates  rapidly  with  the  condition  of  the  fire. 
There  is  also  more  or  less  danger  of  impure  air,  because  in  the 
case  of  even  slight  leaks  between  the  fire  box  and  the  hot  air 
chamber,  soot  and  ashes  tend  to  be  drawn  into  the  heated  air 
and  are  thus  blown  into  the  drying  chamber  where  they  mix 
with  and  deposit  in  the  milk  powder. 

Steam  coils,  enclosed  in  a  vault,  have  been  found  less 
objectionable  in  this  respect.  While  it  is  more  difficult  to  attain 
quite  as  high  a  degree  of  heat  by  this  method,  the  heated  air 
can  be  maintained  more  easily  at  a  uniform  temperature  and 
there  is  no  danger  of  impurities  leaking  into  the  air. 

The  air  is  drawn  into  the  furnace  or  hot  air  vault  from  the 
atmosphere.  It  may  be,  but  usually  is  not,  filtered  by  admitting  it 
through  an  air  filter,  located  at  the  intake,  into  the  hot  air  vault. 
Absorbent  cotton  or  other  similar  pervious  material  may  be  used 
for  this  purpose. 

The  earlier  patents  also  cover  an  air  drying  arrangement  in- 
stalled before  the  air  reaches  the  hot  air  vault.  This  greatly  as- 
sists in  controlling  and  making  uniform  the  results  of  the  drying 
process  from  one  day  to  another,  neutralizing  the  disturbing  ef- 


THE:  SPRAY  PROCESS  309 

feet  of  the  uncontrollable  fluctuations  in  the  humidity  of  the  at- 
mospheric air,  as  affected  by  weather  conditions.  However,  in 
commercial  operation  the  artificial  drying  of  the  atmospheric  air 
is  generally  omitted. 

The  air  may  be  blown  into  the  desiccating  chamber  by  a 
blower  fan,  in  which  case  a  suction  fan  is  frequently  also  installed 
to  draw  the  moisture-laden  air  from  the  desiccating  chamber ;  or  the 
injection  of  the  air  into  the  drying  chamber  may  all  be  taken  care 
of  by  a  strong  suction  fan  located  at  the  air  exhaust  end  of  the 
desiccating  chamber.  It  is  claimed  that  the  double  arrangement 
of  blowing  in  and  drawing  out  of  the  heated  air,  requiring  less 
powerful  suction  at  the  exhaust  end,  minimizes  the  escape  of  milk 
powder  with  the  moisture-laden  air  and  thereby  facilitates  the 
recovery.  The  speed  of  the  drying  action  and  the  exhaustiveness 
of  desiccation  may  be  augmented  by  introducing  the  air  in  such  a 
manner  as  to  produce  a  cyclonic  air  current  moving  spirally  toward 
the  center  of  the  drying  chamber,  where  it  escapes  while  the  milk 
spray  issues  from  the  center,  is  acted  on  by  the  centrifugal  force 
and  moves  tangentially  toward  the  periphery  as  shown  in  the  Gray 
patents. 

The  temperature  of  the  air  as  it  enters  the  desiccating  cham- 
ber is  generally  held  at  from  250°  to  300°  F.,  the  temperature  of 
the  moisture-laden  air  discharging  from  the  drying  chamber  ranges 
from  150°  F.  to  200°  F. 

Spraying  and  Desiccating. — The  drying  is  accomplished  by 
forcing  the  milk  or  condensed  milk,  in  the  form  of  an  atomized 
spray,  into  the  current  of  heated  air  in  such  a  manner,  that  the 
fluid  milk  particles,  or  atoms  of  the  milk  spray,  remain  in  suspen- 
sion sufficiently  long  to  cause  them  to  surrender  substantially  all 
of  their  moisture.  The  dried  particles  or  flakes  of  milk  are  al- 
lowed to  deposit  at  the  bottom  or  sides  of  the  drying  chamber  or  in 
a  separate  collecting  chamber,  from  where  they  are  removed  for 
sifting  and  packing  through  a  hopper,  while  the  moisture-laden  air 
escapes  separately  to  the  outside. 

The  Desiccating  Chamber. — The  desiccating  chambers  in 
commercial  use  vary  considerably  in  size  and  in  shape,  as  well  as 
in  arrangement  of  spray  nozzles  and  intake  and  outlet  of  heated 
air. 


310  THE  SPRAY  PROCESS 

Most  of  these  chambers  are  rectangular,  measure  from  about 
12  feet  in  length,  width  and  height  upward  to  much  larger  dimen- 
sions. Some  are  longer  than  they  are  wide  and  others  are  much 
higher  than  they  are  wide  and  long.  Still  others  are  of  the  circu- 
lar type,  resembling  small  silos,  and  some  are  cone-shape. 

The  desiccating  chambers  are  usually  completely  lined  with 
tin  plate  on  the  inside,  making  them  air  tight  or  nearly  so.  In 
order  to  prevent  waste  of  heat  by  radiation  through  the  walls,  top 
and  bottom,  they  must  be  properly  insulated.  This  is  generally 
done  with  asbestos  sheeting. 

Spray  Nozzles. — The  milk  enters  the  desiccating  chamber 
through  one  or  more  spray  nozzles,  under  a  pressure  of  about 
3,000  pounds.  The  spray  nozzles  are  generally  located  in  the  side 
of  the  drying  chamber  in  close  proximity  to  the  top,  so  as  to  give 
the  spray  particles  as  far  a  distance  to  fall  through  the  heated  air 
as  the  height  of  the  chamber  permits.  Or  the  spray  nozzle  may  be 
located  in  or  near  the  center  of  the  drying  chamber,  in  its  upper 
portion,  in  which  case  the  spray  issues  outward  radially,  or  is  blown 
out  of  the  nozzle  tangentially  by  giving  the  spray  nozzle  a  rotary 
motion. 

When  more  than  one  spray  nozzle  is  used,  the  multiple  noz- 
zles are  either  arranged  in  a  straight  row  along  one  side,  or  they 
may  be  distributed  over  two  or  over  all  four  sides  of  the  desic- 
cating chamber. 

Different  types  of  spray  nozzles  or  atomizers  are  used.  In 
some  hot  air  under  pressure,  or  steam,  propels  and  blows  the  milk 
through  the  nozzle  on  a  similar  principle  as  the  boiler  water  in- 
jector. In  other  cases  the  spray  nozzle  consists  of  a  heavy  black 
iron  cap,  about  one  and  one-quarter  inch  long  and  with  a  one-half 
inch  threaded  bore.  This  cap  is  screwed  on  to  the  end  of  the 
milk  pipe,  or  its  laterals.  In  the  center  of  the  closed  end,  the  cap 
has  a  very  fine  opening  with  a  diameter  of  from  one-half  to  one 
millimeter  (.02  to  .04  inch).  A  small  brass  disc,  about  one-quar- 
ter inch  thick  and  snugly  fitting  into  the  iron  cap,  lays  against 
the  closed  end  of  the  cap  and  covers  the  small  orifice.  This  brass 
disc  carries  two  minute  spiral  grooves  at  its  periphery,  through 
which  the  milk  under  pressure  is  forced  between  disc  and  cap 


THE  SPRAY  PROCESS  311 

and  escapes  through  the  small  orifice  in  the  cap,  forming  a 
fine  spray  or  mist. 

The  small  orifice  through  which  the  milk  spray  enters  the 
desiccating  chamber  increases  in  size  by  usage  due  to  wear,  and 
necessitates  the  frequent  replacing  of  the  old  caps  or  nozzles  by 
new  ones.  When  in  operation,  these  spray  nozzles  at  times  be- 
come clogged  and  must  be  changed  for  cleaning.  It  is  necessary, 
therefore,  for  the  operator  to  supervise  the  process  continually, 
making  sure  that  all  the  spray  nozzles  function  properly,  so  as  to 
secure  maximum  efficiency  and  speed  of  desiccation. 

In  order  to  facilitate  the  changing  of  spray  nozzles  while  desic- 
cation is  in  progress,  the  nozzles  are  so  placed  as  to  connect  with 
the  milk  pipe  on  the  outside  of  the  desiccating  chamber,  the  nipples 
carrying  the  spray  nozzles  connecting  with  the  milk  supply  pipe  by 
means  of  Barco  joints  (loose  joints),  can  be  turned  in  all  directions 
sufficiently  to  withdraw  the  nozzles  from  the  desiccating  chamber 
independently  and  at  any  time  during  the  desiccating  operation. 

Spray  Pumps. — In  order  to  maintain  a  uniform  efficiency  of 
desiccation  and  to  secure  a  uniform  fineness  of  spray,  it  is  im- 
portant that  the  pressure  of  the  milk  should  be  uniform.  To  ac- 
complish this  requires  a  special  type  of  pump.  The  pumps  best 


Fig-.  107.     Hig-li  pressure  pump  for  spraying1  milk 
Courtesy  of  Union  Steam  Pump  Co. 

suited  for  this  purpose  are  three  cylinder  pumps  with  large,  heavy 
valves  and  with  extra  deep  stuffing  boxes  that  can  be  packed  with 
one-half  inch  packing  rings,  and  special,  heavily  bolted  glands  that 
can  be  readily  adjusted  when  the  pump  is  running. 

The    triple    cylinder    arrangement    insures    a    steady    pressure 


312  THE:  SPRAY  PROCESS 

and  continuous  flow  through  the  spray  nozzles  and  the  deep  stuf- 
fing boxes  enhance  the  tightness  of  the  seal.  The  hardening  of 
condensed  milk  on  the  plungers  is  prevented  by  an  open  pot  water- 
seal  which  completely  merges  the  stuffing  boxes,  the  water  serving 
to  both  cool  and  lubricate  the  packing  and  to  prevent  its  being  hard- 
ened by  absorbing  condensed  milk.  While  the  pump  is  in  operation 
a  small  stream  of  cold  water  is  allowed  to  run  into  this  water  pot 
and  to  overflow  through  a  suitable  opening. 

These  pressure  pumps  should  also  be  provided  with  proper 
relief  or  overflow  valves,  so  as  to  avoid  the  danger  of  excessive 
pressure  and  variation  in  the  spray,  in  case  several  of  the  spray 
nozzles  should  become  clogged  simultaneously. 

At  the  finish  of  the  run  of  milk,  a  quantity  of  water  should 
be  pumped  through  these  high  pressure  pumps  and  pipes  and  it 
is  advisable  to  allow  the  pumps  and  pipes  to  stand  full  of  water 
when  they  are  not  in  use,  so  as  to  loosen  and  remove  remnants  of 
condensed  milk,  preventing  their  accumulation  in  the  cylinders  and 
avoiding  difficulties  incident  to  plugging  and  clogging. 

The  pressure  used  at  which  the  milk  is  forced  through  the 
spray  nozzles  varies  from  800  to  3,500  pounds  per  square  inch, 
the  usual  range  of  pressure  employed  fluctuates  between  2,000  and 
3,000  pounds.  The  multiple  nozzles  with  the  fine  openings  require 
less  pressure  to  secure  the  same  atomizing  effect  than  when  fewer 
or  one  large  nozzle  is  used. 

Hot  Air  Intake  and  Discharge. — The  heated  air  enters  the 
drying  chamber  at  points  varying  with  different  types  of  cham- 
bers. Where  the  spray  issues  forth  from  nozzles  located  all  on 
one  side,  the  heated  air  often  is  admitted  through  a  slot  located 
directly  under  the  spray  nozzles  and  the  air  travels  in  the  same 
direction  as  the  spray  and  mixes  with  it. 

In  desiccating  chambers  in  which  the  spray  nozzles  are  in- 
stalled on  all  sides,  the  heated  air  may  enter  near  the  bottom  in 
the  center  of  the  desiccating  chamber,  pass  up  through  and  mix- 
ing evenly  with  the  spray  that  issues  from  all  sides  toward  the 
center.  Or  the  heated  air  may  enter  at  the  top  and  pass  downward 
with  the  spray.  Or  it  may  enter  at  the  periphery  at  various  points 
near  the  top,  in  the  form  of  a  cyclonic  current  moving  spirally  to- 
ward the  center,  and  escaping  in  the  center  through  the  top  of  the 
desiccating  chamber. 


THE  SPRAY  PROCESS  313 

The  arrangement  of  the  exit  of  the  moisture-laden,  spent  air 
also  differs  with  different  drying  chambers.  In  many  cases,  espe- 
cially where  the  heated  air  and  spray  enter  at  one  side,  the  exit 
of  the  moisture-laden  air  is  on  one  side,  in  this  case  on  the  side 
opposite  that  of  the  intake.  In  other  cases  the  spent  air  escapes 
at  the  top  and  in  still  others  near  the  bottom  of  the  desiccating 
chamber. 

Hausbrand1  points  out  that  the  air  always  enters  the  desic- 
cating room  hotter  than  it  leaves  and  that  the  spent  air  is  usually 
more  completely  moisture-saturated  than  the  incoming  air.  The 
density  of  the  spent  air  therefore  is  greater  than  that  of  the  air 
at  the  intake.  The  spent  air  is  heavier.  It  has,  consequently,  an 
inclination  to  pass  downward.  Hausbrand  accordingly  holds,  that 
in  vertical  drying  rooms  the  direction  of  the  currents  of  air  should 
be  from  top  to  bottom,  since  the  movement  is  then  more  uniform 
than  when  the  heated  air  enters  below  and  at  once  takes  the  shortest 
path  to  the  upper  exit,  without  coming  in  contact  with  all  the  dry- 
ing material. 

It  is  important  that  the  drying  room  be  protected  against 
the  entry  of  air  from  outside.  The  walls  must  be  free  from  leaks, 
the  peep  holes  or  sight  glasses,  the  doors  and  the  shutters  in  the 
hopper  at  the  bottom,  must  fit  tightly. 

The  outgoing  air,  in  a  properly  operating  desiccating  cham- 
ber, should  have  a  temperature  considerably  lower  than  the  incom- 
ing air.  As  previously  stated,  it  usually  is,  and  it  is  desirable  that 
it  should  be  below  200°  F.,  and  preferably  not  above  about  150°  F. 
The  lowering  of  the  temperature  of  the  heated  air  in  the  desiccat- 
ing chamber  is  due  to  the  cooling  effected  by  the  rapid  evaporation 
of  the  moisture  from  the  spray  of  milk.  This  cooling  effect  in 
turn  protects  the  milk  solids  against  changes  resulting  from  contact 
with  the  hot  air,  and  assists  in  preserving  their  .original  solubility. 

Recovery  of  Desiccated  Milk. — Because  of  the  extreme  fine- 
ness and  lightness  of  the  milk  powder  made  by  the  spray  process 
of  desiccating  milk,  a  certain  portion  of  the  most  flaky  and  fluffy 
particles  escapes  from  the  desiccating  chamber  with  the  outgoing 
air.  As  previously  stated,  the  proportion  of  powder  that  thus 
escapes  varies  greatly  with  the  degree  of  flakiness  or  granulation 


1  Hausbrand,   Drying  by  Means  of  Air  and    Steam,    1901. 


314  THE;  SPRAY  PROCESS 

of  the  product.  But  even  in  the  case  of  quite  granular  powders 
a  very  appreciable  portion  leaves  the  desiccating  chamber.  Again, 
efforts  have  been  made  to  prevent  this  escape  of  milk  powder  by 
extending  the  length  of  the  desiccating  chamber,  thereby  augment- 
ing the  distance  between  the  intake  and  exit  of  the  hot  air.  This 
arrangement  subjects  the  dried  particles  over  a  longer  distance  to 
the  gravity  force,  their  opportunity  to  drop  to  and  deposit  on  the 
bottom  of  the  desiccating  chamber  before  being  caught  in  the  out- 
going air  current  is  augmented,  and  the  tendency  for  escape  is 
diminished.  In  other  cases,  see  Gray  patent,  the  intake  and  dis- 
charge of  the  air  and  the  direction  of  the  particles  of  milk  are  so 
arranged  that  the  moisture-laden  air  escapes  in  the  center  while  the 
milk  spray  moves  tang'entially  toward  the  periphery,  thus  making 
for  minimum  escape  and  maximum  recovery  of  the  powder. 

At  best,  however,  there  is  need  of  provisions  to  recover  milk 
powder  carried  off  in  the  air  currents  escaping  from  the  desiccating 
chamber,  and  diverse  contrivances  have  been  designed  and  are  in  use 
in  milk  powder  factories  for  this  purpose. 

These  arrangements  for  the  purpose  of  reclaiming  or  recover- 
ing the  milk  powder  are  known  as  "dust  collectors."  They  are 
similar  in  principle  to  those  used  in  flower  mills.  Some  of  these 
dust  collectors  now  in  commercial  use  are  guaranteed  to  accom- 
plish 99.9  per  cent  recovery  of  such  products  as  corn  starch,  wheat 
flour  and  the  like. 

They  chiefly  consist  of  vaults  or  drums  or  other  containers 
into  which  the  suction  fan,  located  at  the  air  exit  end  of  the  dry- 
ing chamber,  discharges  the  outgoing  air.  These  vaults  are 
equipped  with  a  series  of  canvas  screens  or  bags  on  which  the  par- 
ticles of  milk  powder  floating  in  the  outgoing  air,  are  deposited, 
and  from  which  by  mechanical  shaking  or  otherwise,  the  escaping 
milk  powder  is  reclaimed  and  recovered. 

In  some  factories  a  part  of  the  recovery  equipment  consists 
of  a  so-called  cyclone.  This  is  usually  a  cylindrical  receptacle 
with  cone-shaped  bottom.  The  air  escaping  from  the  drying  cham- 
ber is  blown  into  this  cyclone  with  great  force  and,  being  thrown 
against  its  walls,  drops  at  least  a  portion  of  the  fine,  dust-like  milk 
powder  it  contains. 


COMPOSITION  AND  PROPERTIES  OF  MILK  POWDERS         315 

Bolting. — The  powdered  milk  resulting  from  the  spray  dry- 
ing process  of  desiccation  requires  no  grinding.  It  is  very  floury 
in  its  physical  make  up,  and  after  sifting  it  is  ready  to  be  packed. 

Packing  of  Milk  Powder. — The  dried  milk  is  put  on  the 
market  in  packages  of  various  types,  such  as  fibre  containers,  tin 
cans  and  barrels.  The  sizes  vary  from  8  ounce  packages  to  200 
pound  barrels.  Of  the  small  size  packages  the  10  pound  can  with 
friction  top  predominates.  The  barrels  vary  some  in  net  weight 
with  the  process  of  manufacture  used,  the  granular  product  of 
the  dough-drying  and  film-drying  processes  being  heavier  than  the 
flaky  product  of  the  spray-drying  process. 

The  bulk  of  milk  powder  reaches  the  market  in  barrels ;  these 
are  paper  lined,  similar  as  sugar  barrels. 

CHAPTER  XXVII. 

COMPOSITION  AND  PROPERTIES  OF 
MILK  POWDERS. 

Chemical  Composition  of  Milk  Powders. — The  chemical 
composition  of  milk  powders  varies  principally  with  the  percent- 
age composition  of  the  original  milk  from  which  the  powder  is 
made,  and  to  some  extent  with  the  process  of  desiccating. 

The  percentage  composition  of  the  fluid  milk  is  controlled 
primarily  by  locality  and  season  of  year,  as  determined  by  breed, 
period  of  lactation  and  feed  of  the  cows.  For  these  reasons  milk 
powders  made  by  the  same  process,  but  in  different  localities  and 
at  different  seasons  of  the  year,  often  show  very  considerable 
variations  in  their  percentage  composition. 

Effect  of  Atmospheric  Conditions. — The  atmospheric  con- 
dition, especially  with  reference  to  humidity  of  the  air,  has  a 
further,  frequently  quite  material  effect  on  the  chemical  composi- 
tion of  the  powder  from  the  standpoint  of  dryness  or  moisture 
content.  Experience  has  amply  demonstrated  that  when  there  is 
a  high  degree  of  humidity  in  the  atmosphere,  the  resulting  milk 
powder  shows  a  higher  per  cent  moisture  than  when  made  on  a 
clear,  dry  day. 


316         COMPOSITION  AND  PROPERTIES  OF  MILK  POWDERS 

Effect  of  Process  of  Manufacture. — The  influence  of  the 
process  of  manufacture  on  the  composition  of  the  milk  powder 
refers  primarily  to  modifications  of  the  milk  prior  to  desiccation, 
although  the  method  of  desiccation  itself  also  exerts  a  limited 
effect. 

The  greater  the  percentage  of  butterfat  to  which  the  original 
milk  has  been  standardized  or  modified,  the  lower  must  necessa- 
rily be  the  percentage  of  solids  not  fat,  and  this  same  fact  is  true 
also  of  the  finished  powder.  Hence  the  milk  powders  may  vary 
from  say  one  per  cent  of  fat  and  possibly  over  95  per  cent  of 
solids  not  fat  in  the  case  of  skim  milk  powder,  to  over  70  per  cent 
of  fat  and  less  than  30  per  cent  of  solids  not  fat  in  the  case  of 
cream  powder.  Whole  milk  powders  generally  contain  from  about 
26  to  29  per  cent  fat. 

The  degree  of  dryness,  or  per  cent  of  moisture,  aside  from 
atmospheric  conditions  is  largely  governed  by  the  process  of  desic- 
cation. Generally  speaking,  milk  powders  manufactured  by  the 
spray-drying  process  contain  less  moisture  than  those  made  by  the 
film-drying  and  dough-drying  processes. 

The  spray-drying  process,  at  its  present  state  of  perfection, 
makes  possible  the  removal  of  all  but  a  very  small  percentage  of 
moisture.  Spray  powders  containing  as  low  as  one  per  cent 
moisture  are  quite  possible ;  in  fact,  the  moisture  content  of  these 
powders,  as  found  in  commerce,  ranges  from  about  .5  per  cent  to 
3.5  per  cent,  averaging  about  1.5  to  2.5  per  cent. 

The  powders  resulting  from  the.  film-drying  processes  generally 
contain  from  about  3  to  6  per  cent  moisture. 

Some  milk  powders,  especially  certain  brands  of  foreign  man- 
ufacture, and  particularly  those  of  the  dough-drying  process,  also 
contain  added  sucrose. 


COMPOSITION  AND  PROPERTIES  OF  MILK  POWDERS         317 


Chemical  Composition  of  Milk  Powders. 


Analyses    Made    or 
Reported  by 

Water 

% 

Butter- 
fat 

% 

Protein 

% 

Milk 
Sugar 

% 

Ash 

% 

Cane 
Sugar 
% 

Whole  milk  powders: 

Richmond1    
Richmond1    

6.39 
4.92 

27.35 
27.98 

27.48 
24.59 

31.42 
34.16 

6.00 
6.24 

Vis 

Richmond1    

474 

29.16 

26.66 

32.24 

5.63 

C.  Huyge2   .  . 

3.62 

26.75 

32.06 

31.90 

5.67 

.... 

Larsen  &  White8  

1.40 

29.20 

26.92 

36.48 

6.00 

.... 

Otakar  Laxa4   

4.07 

25.00 

24.84 

35.75 

620 

3.13a 

Merrell-Soule  Co.5  .... 
Part   skim   milk 
powders  : 
Richmond1 

1.50 
5.15 

28.20 
19.90 

26.67 
31.10 

37.88 
34.96 

5.75 
7.11 

.... 

C.  Huvs'e'2  . 

5.01 

15.26 

38.39 

34.67 

6.67 

C.  Huy^e2  

8.30 

13.00 

30.57 

48.85 

7.28 

.... 

Larsen  &  White3  
Otakar  Laxa4   
Otakar  Laxa4 

5.00 
5.46 
4.80 

15.12 
21.96 
17.13 

33.30 
25,69 
29.88 

39.70 
40.93 
40.72 

6.90 
5.74 
6.84 

U6a 
5.08a 

Otakar  Laxa4  

5.85 

15.72 

30.95 

40.67 

6.06 

1.46a 

Merrell-Soule  Co.5  .... 
Skim  milk  powders: 
Richmond1    

2.12 

3.55 

14.20 

2.55 

32.26 

35.45 

44.41 
45.60 

7.01 
7.89 

' 
2.80 

C.  Huvge2  

7.40 

1.00 

37.28 

46.30 

8.00 

.... 

Larsen  &  White3 

7.00i 

1.00 

37.00 

47.00 

8.00 

Otakar  Laxa4   ... 

7.15 

1.57 

33.29 

47.23 

8.03 

Stocking"5   

2.40 

1.35 

37.70 

49.94 

8.21 

Mojonnier  P>ros.  Co.0.  . 
Mqjonnier  Bros.  Co.6.  . 
Mojonnier  Bros.  Co.6.  . 
Cream  powders: 
Merrell-Soule  Co.5  
Merrell-Soule  Co.5  
Merrell-Soule  Co.5  .  . 

3.39 
1.72 
1.00 

.80 
.66 
.56 

1.25 
1.15 
1.97 

50.40 
65.15 
71.15 

33.94 
35.01 

34.75 

19.19 
13.42 
11.12 

50.88 
52.24 
51.92 

25.45 
17.86 
14.74 

7.87 
8.03 
8.24 

4.16 
2.91 
2.43 

.... 
.... 

1  Richmond,  Dairy  Chemistry,  1914. 

2  C.   Huyge.     La   Poudre   du  lait,   Revue  ge"nerale   du  lait.  V  ol   3,  No.   14, 
1904.     Also  Leach   Food  Analyses. 

3  Larsen  &  White.     Dairy  Technology,  1913. 

4  Otakar  Laxa.     Berichte  der  laktologischen  Anstalt  der  k.  k.  bohmischen 
technischen  Hochschule  in  Prag,  Vol.  VIII.,   1917. 

8  Merrell-Soule   Co.      Descriptive   Bulletin   Concerning   Merrell-Soule   Pow- 
dered Milk,  1918;  also  Stocking,  Manual  of  Milk  Products,   1919. 
8  Mojonnier  Bros.  Co.     Analysis  by  request  of  author,   1919. 
a  Hydrocarbons  in  ash. 


COMPOSITION1    AND    PROPERTIES    OF    MlLK    POWDERS 


Solubility  of  Milk  Powders.  —  Jf  milk  powders  are  to  take 
the  place  of  fresh  milk  or  condensed  milk  on  the  table  of  the  con- 
sumer, and  for  most  of  the  industrial  uses  to  which  they  are  being 
put,  they  must  be  readily  soluble.  One  of  the  greatest  obstacles 
in  the  progress  of  the  milk  powder  industry  has  been  that  the 
dried  milk  of  most  of  the  processes  failed  to  be  readily  and  com- 
pletely soluble..  Earlier  processes  prescribed  the  admixture  to 
the  milk  of  alkalies  in  order  to  preserve  the  solubility  of  the  pro- 
teids,  which  otherwise  were  rendered  insoluble  by  the  high  heat 
of  the  respective  processes.  It  is  obvious  that  a  dried  milk,  the 
solubility  of  which  can  be  retained  only  by  the  admixture  of  al- 
kalies, is  a  poor  substitute  for  milk,  and  the  very  principle  of  add- 
ing chemicals  to  a  food  product  like  milk,  is  contrary  to  our  ideal 
of  successful  manufacture  of  high  quality  of  product. 

The  term  "Solubility"  is  here  used  in  the  broader  sense  of 
the  word.  Milk  is  not  a  true  solution.  It  is  part  solution  and 
part  emulsion.  "Solubility"  here  implies  a  powder,  in  which  those 
constituents  which  are  in  complete  solution  in  normal  fluid  milk, 
have  retained  their  original  solubility,  such  as  the  sugar  of  milk, 
and  in  which  those  constituents  which  are  present  in  normal  fluid 
milk  in  the  form  of  an  emulsion,  as  is  the  case  with  the  casein, 
fat  and  part  of  the  ash,  have  retained  their  original  emulsifying 
power.  In  short,  the  term  "solubility,"  as  used  in  this  discussion, 
means  those  attributes  of  the  milk  powder  that  enable  the  pow- 
der, when  mixed  with  water,  to  again  form  a  solution  and  emulsion 
of  a  character,  physically  and  mechanically,  similar  to  that  of  nor- 
mal fluid  milk. 

The  solubility  of  milk  powders  varies  principally  with  the 
quality  of  the  fluid  milk  and  with  the  process  of  manufacture. 

By  quality  of  milk,  as  here  referred  to,  is  meant  chiefly  the 
acidity.  The  combination  of  the  heat  of  desiccation  and  of  high 
acidity,  tends  to  rob  the  protein  and  ash  constituents  of  the  re- 
sulting powder  of  their  natural  solubility.  The  higher  the  de- 
gree of  acid  in  the  fluid  milk,  the  lower  will  be  the  solubility  of 
the  powder.  The  fresher  and  sweeter  the  milk  at  the  time  of  desic- 
cation, the  more  soluble  will  be  the  powder,  other  factors  being  the 
same. 

For  this  reason  many  milk  powder  factories  are  endeavoring 


COMPOSITION  AND  PROPERTIES  OF  MILK  POWDERS         319 

to  receive  their  fluid  milk  twice  daily,  and  some  are  using  alkaline 
neutralizers  in  order  to  reduce  the  acidity  of  the  milk  before  desic- 
cation. 

One  fundamental  reason  why  even  slight  increases  in  acidity 
do  very  markedly  reduce  the  solubility  of  the  finished  powder,  lies 
in  the  fact  that  the  high  degree  of  concentration  necessarily  mul- 
tiplies the  percentage  of  acid,  and  with  it  the  solubility-destroying 
effect  of  the  heat  of  desiccation. 

The  process  of  manufacture  controls  the  solubility  of  the  milk 
powder  chiefly  by  the  degree  of  heat  to  which  the  milk  is  exposed 
and  by  the  manner  in  which  the  heat  is  applied. 

In  the  film  process  of  drying,  for  instance,  the  milk  is  exposed 
to  the  heated  cylinder  charged  with  steam  under  pressure,  and  con- 
sequently it  is  subjected  to  temperatures  far  exceeding  that  of  the 
boiling  point  of  water.  This  high  heat  does  materially  reduce  the 
solubility  of  the  resulting  powder,  though  this  unfavorable  effect 
may  be  minimized  to  some  extent  by  having  the  cylinders  operate 
in  a  vacuum  chamber  under  reduced  pressure. 

In  the  case  of  the  spray-drying  process,  the  milk  is  not  exposed 
to  a  steam-heated  metal  surface.  The  fact  that  the  air  entering  the 
spray-drying  chamber  may  have,  and  usually  does  have,  a  tempera- 
ture of  from  275  degrees  F.  to  over  300  degrees  F.,  appears  to  not 
materially  affect  the  solubility  of  the  resulting  powder. 

In  the  spray-drying  process  the  evaporation  of  the  moisture  in 
the  atomized  spray  is  so  rapid  that  it  brings  about  a  marked  cooling 
effect,  and  it  is  believed  that  the  milk  solids  are  kept  in  a  relatively 
cool  condition  until  they  have  surrendered  substantially  all  of  their 
moisture. 

This  protection  of  the  milk  against  the  solubility-destroying 
action  of  heat  appears  to  be  especially  insured  by  the  process  of 
the  Gray  patent,  in  which  the  coolest  strata  of  the  heated  air  "only 
come  in  contact  with  the  incoming  moisture-laden  milk,  and  by  the 
time  the  milk  particles  enter  the  zone  of  the  hot  incoming  air  they 
have  surrendered  the  bulk  of  their  moisture. 

That  a  marked  cooling  effect  does  take  place  in  the  drying 
chamber  is  further  borne  out  by  the  fact  that  the  moisture-laden  air 
escaping  from  the  drying  chamber  has  a  temperature  very  much 
lower  than  the  entering  air.  The  outgoing  air  of  a  properly  operated 


320         COMPOSITION  AND  PROPERTIES  OF  MILK  POWDERS 

spray-drying  chamber  usually  has  a  temperature  of  from   150  to 
about  180  degrees  F. 

In  the  spray-drying  process  it  is  customary  to  heat  the  fluid 
milk  or  the  condensed  milk  to  not  to  exceed  150  degrees  F.,  and  it 
appears  that  when  this  is  done  the  milk  solids  are  not  exposed  to 
temperatures  materially  higher  than  150  degrees  F.  until  they  have 
given  off  their  moisture ;  in  fact,  it  is  possible  that  at  least  during 
the  early  stages  of  desiccation  they  are  actually  cooled  by  their 
rapid  surrender  of  moisture. 

Experimental  study  has  demonstrated  that,  when  a  certain  de- 
gree of  concentration  has  been  exceeded,  exposure  to  high  heat  de- 
stroys the  solubility  of  the  protein  constituents  of  the  milk.  This 
is  a  matter  of  common  knowledge  to  the  operator  of  the  sterilizer 
in  the  manufacture  of  evaporated  milk.  In  the  spray-drying  process 
the  change  from  high  concentration  of  the  milk  in  the  liquid  state,  to 
complete  dryness,  is  so  instantaneous  that  no  damage  is  done  and 
when  once  dry,  exposure  to  heat  does  no  further  harm. 

The  solubility  of  the  powder  resulting  from  the  spray-drying 
process  may  be  materially  reduced,  however,  if  the  fluid  milk, 
prior  to  desiccation,  is  heated  to  temperatures  considerably  in  ex- 
cess of  150  degrees  F. 

The  powders  of  the  properly  operated  spray-drying  process  are 
practically  completely  soluble  in  cold  water.  The  powders  of  the 
film-drying  process  require  hot  water  for  their  solution  and  even  in 
hot  water  they  fall  short  slightly,  but  unmistakably,  of  complete 
solution. 

The  relative  solubility  of  spray-  and  film-dried  powders  is 
shown  in  the  following  table : 


COMPOSITION  AND  PROPERTIES  OF  Miuc  POWDERS 


321 


Solubility  of  Milk  Powders  of  Film-Drying  Process,  and 
of  Spray-Drying  Process. 


Process  of  Desiccation 

In  Cold  Water 
78.5°  F. 

In  Hot  Water 
210°  F. 

Per  Cent 
In 
Solution 

Per  Cent 
of 

Powder 
Dissolved 

Per  Cent 
in 
Solution 

Per  Cent 
of 
Powder 
Dissolved 

Total   Solids 


Film-process  powders: 

Skim  milk  powder.  .  .    . 

3.94 
3.46 

5.61 
5.09 

69.61 
61.13 

99.12 
88.16 

4.42 
4.53 

5.76 
5.33 

78.09 
80.03 

101.76 
94.17 

Cream  powder   

Spray-process  powders  : 

Skim  milk  powder  (milk 
to     150    degrees    F. 
desiccation) 

heated 
before 

Skim  milk  powder  (milk 
to    210    degrees    F. 
desiccation) 

heated 
before 

Protein 

Film-process  powders: 
Skim  milk  powder       ... 

41 

.65 

Cream  powder  

49 

1.62 

Spray-process  powders: 

Skim  milk  powder  (milk  heated 
to     150    degrees    F.    before 
desiccation) 

200 

1.97 

Skim  milk  powder  (milk  heated 
to    210    degrees     F.     before 
'     desiccation) 

1.47 

1.74 

The  solubility  tests,  the  results  of  which  are  recorded  in  the 
foregoing  table,  were  made  as  follows : 

Two  samples  of  film-process  powders  and  two  samples  of  spray- 
process  powders  were  used.  Twelve  grams  of  each  powder  was 
added  to  200  cc.  of  water  at  a  temperature  of  78.5  degrees  F.  The 
four  samples  were  placed  into  a  mechanical  shaker  and  shaken  for 
ten  minutes. 

After  shaking,  100  cc.  of  each  lot  was  poured  through  a  paper 
filter  and  the  filtrate  analyzed  for  percentage  of  total  solids. 

The  remaining  100  cc.  of  each  lot  was  heated  to  the  boiling 


322         COMPOSITION  AND  PROPERTIES  OF  MILK  POWDERS 

point  and  held  there  for  five  minutes.  The  water  lost  by  evapora- 
tion was  replaced.  The  hot  solutions  were  then  filtered  and  analyzed 
for  total  solids. 

The  results  of  the  above  tests  show  that  the  spray-process 
powder  when  made  from  milk  that  was  not  heated  above  150  de- 
grees F.  before  desiccation,  had  the  power  of  returning  into  an 
emulsion  in  cold  water  that  would  filter  in  a  similar  manner  and 
would  pass  through  the  filter  with  a  similar  degree  of  completeness 
as  ordinary  milk.  The  powder  was  substantially  completely  soluble. 

When  made  from  milk  that  had  been  heated  to  the  boiling  point, 
the  spray-process  powder  lost  slightly  over  10  per  cent  of  its  solu- 
bility. About  one-half  of  this  loss  was  recovered  upon  heating  the 
water  and  powder  mixture  to  the  boiling  point. 

The  film-process  powder  in  cold  water  went  into  a  filterable 
emulsion  to  the  extent  of  from  60  to  70  per  cent  of  the  powder 
added,  and  in  hot  water  to  the  extent  of  from  78  to  80  per  cent  of 
the  powder  added. 

The  very  marked  difference  in  solubility  of  the  powders  from 
the  two  processes  could  be  readily  observed  also  without  chemical 
analysis.  When  the  solutions  of  the  film-process  powders  were 
allowed  to  remain  at  rest  in  test  tubes  there  would  always  gather 
a  very  considerable  deposit  of  solid  matter  in  the  bottom.  This  was 
the  case  in  both  hot  and  cold  water,  but  the  deposit  was  very  con- 
siderably more  voluminous  in  the  cold  mixture  than  in  the  hot 
mixture. 

In  the  case  of  the  spray-process  powders  no  such  deposit  of 
solid  matter  could  be  detected,  neither  in  the  hot  nor  in  the  cold 
mixtures.  , 

It  is  further  interesting  to  note  that  the  percentage  of  protein 
found  in  the  filtrates  from  all  the  powders  with  the  exception  of 
the  hot  solution  from  the  film-process  cream  powder,  followed  very 
closely  the  percentage  of  total  solids  in  the  same  filtrates.  This 
suggests  very  obviously  that  the  degree  to  which  the  solubility,  or 
better  the  power  of  the  milk  powder  to  return  to  the  character  of 
the  original  milk,  is  impaired  by  the  process  of  desiccation,  is  largely 
controlled  by  and  depends  on  the  extent  to  which  the  process  of 
desiccation  changes  the  physical  properties  of  the  protein  of  milk. 

Miscibility  and  Readiness  of  Solution  of  Milk  Powders. — 
The  rapidity  and  readiness  with  which  milk  powders  go  into  so- 


COMPOSITION  AND  PROPERTIES  OF  Miut  POWDERS         323 

called  solution  is  a  factor  which  does  not  always  depend  on  their 
actual  solubility. 

Other  conditions  being  the  same,  it  is  obvious  that  the  finer  the 
particles  of  the  powder  the  more  rapidly  will  it  dissolve.  This  fact 
is  based  on  the  well-known  physical  law  that  the  smaller  a  body  the 
larger  is  its  surface  in  proportion  to  its  cubic  contents.  The  sur- 
faces of  two  spheres  are  to  each  other  as  the  squares  of  their  diame- 
ters and  the  cubic  contents  of  two  spheres  are  to  each  other  as  the 
cubes  of  their  diameters.  This  is  clearly  demonstrated  in  the  fol- 
lowing example : 

One  sphere  has  a  diameter  of  2  inches  and  the  other  sphere  has 
a  diameter  of  4  inches.  The  surfaces  and  the  cubic  contents  of 
these  spheres  are  as  follows : 


Fig*.  108. 

Sphere  with  Sphere  with 

2-inch  dia.  4-inch  dia. 

Surfaces  2x2  =  4  4X4=  16 

Cubic  contents  =2x2X2  =  8  4X4X4  =  64 

The  surface  of  the  sphere  with  the  4-inch  diameter  is  four 
times  as  large  as  the  surface  of  the  sphere  with  the  2-inch  diameter. 
But  the  cubic  content  of  the  sphere  with  the  4-inch  diameter  is 
eight  times  as  great  as  the  cubic  content  of  the  sphere  with  the  2-inch 
diameter. 

And  again,  the  cube  and  circular  shape  of  a  body  has  a  smaller 
surface  than  the  oblong  and  flake  shape  body. 

The  greater  the  area  or  surface  of  a  body  with  a  given  cubic 
content,  the  more  surface  is  exposed  to  the  solvent  and  the  more 
rapidly  will  it  dissolve.  Therefore,  the  finer  and  more  flaky  the 
particles  of  milk  powder,  the  more  readily  and  more  rapidly  will 
they  dissolve. 

The  spray-process  powders  usually  are  finer  and  more  flaky 


324         COMPOSITION  AND  PROPERTIES  OF  MILK  POWDERS 

than  the  film-process  powders,  hence  the  former  should  go  in  solu- 
tion more  rapidly  than  the  latter. 

The  above  facts  concerning  the  relation  of  fineness  and  flakiness 
of  milk  powder  to  ease  and  speed  of  solution  prevail  to  a  certain 
point.  When  that  point  is  exceeded  mechanical  handicaps  enter 
into  the  results  that  tend  to  retard  solution,  at  least  in  the  beginning. 
In  the  case  of  excessively  fine  and  flaky  milk  powders,  the  exposed 
surfaces  are  so  great  and  the  particles  so  small  that  when  the  powder 
is  placed  into  water,  the  rapid  solution  of  the  powder  that  comes 
into  immediate  contact  with  the  water  causes  the  powder  to  run 
together  and  paste,  forming  a  pasty  coating  around  the  remainder 
of  the  powder.  This  coating  hinders  and  retards  the  penetration  of 
the  powder  by  the  water  and  thereby  renders  complete  solution 
slower,  at  least  at  the  start. 

This  difficulty  is  generally  not  experienced  with  the  film-process 
powders,  which  are  of  a  granular  nature.  It  can  be  largely  avoided 
in  the  case  of  the  spray-process  powders  by  so  adjusting  the  orifice 
of  the  spray  nozzles  and  the  pressure  of  the  milk,  as  to  increase  the 
coarseness  of  the  spray.  The  coarser  the  spray  the  less  flaky  and 
the  more  granular  the  powder.  High  pressure  and  small  orifice  in 
spray  nozzles  produce  a  very  fine  spray  and  a  flaky  powder.  Low 
pressure  and  large  orifice  in  spray  nozzles  produce  a  less  fine  spray 
and  a  more  granular  powder. 

The  concentration  of  the  milk  at  the  time  of  spraying  also  in- 
fluences the  coarseness  or  fineness  of  the  spray  to  a  considerable 
extent.  Other  conditions  being  the  same,  the  higher  the  concentra- 
tion of  the  milk  at  the  time  of  spraying  the  coarser  the  spray  and 
the  less  flaky  and  the  more  granular  the  resulting  milk  powder. 
When  the  milk  is  sprayed  before  previously  condensing  it,  a  finer 
and  flakier  powder  is  produced  than  when  the  milk  is  first  con- 
densed at  the  ratio  of  about  4:1,  and  the  condensed  milk  is  sprayed, 
always  assuming,  however,  that  other  conditions,  such  as  orifice  of 
spray  nozzle  and  pressure  of  milk  be  the  same.  It  is  possible,  even 
by  spraying  the  fluid,  uncondensed  milk,  to  produce  a  powder  that 
is  distinctly  granular,  by  the  proper  adjustment  of  the  above  factors. 

The  miscibility  of  the  dried  milk  with  water  depends,  aside 
from  its  solubility,  readiness  of  solution  and  character  of  the  protein, 
on  the  physical  condition  of  its  butter  fat.  If  the  process  employed 
is  such  as  to  destroy  the  globular  form  of  the  fat  globules,  it  is 


COMPOSITION  AND  PROPERTIES  OF  Miuc  POWDERS         325 

impossible  to  reduce  the  dried  milk  to  a  homogeneous  fluid,  similar 
to  normal  fresh  milk.  The  fat  in  such  milk  will  rise  to  the  surface 
quickly,  similar  to  the  f2t  in  a  mixture  of  oil  and  water. 

Keeping  Quality  of  Milk  Powders. 

Moisture  Content. — One  of  the  fundamental  reasons  for 
which  milk  is  reduced  to  a  dry  powder  lies  in  the  efforts  of  the 
manufacturer  to  preserve  it. 

Bacteria  and  other  micro-organisms  require  moisture  to  grow, 
thrive  and  accomplish  their  work  of  decomposing  the  substances  in 
which  and  on  which  they  live.  In  the  absence  of  moisture  bacterial 
action  ceases. 

In  properly  desiccated  milk  powders,  such  as  are  now  manu- 
factured and  placed  upon  the  market,  the  percentage  of  moisture 
has  been  reduced  to  a  point  that  precludes  the  possibility  of  bac- 
terial decomposition.  If  these  desiccated  milk  powders  are  packed 
and  stored  in  such  a  manner  as  to  protect  them  against  dampness, 
they  may  reasonably  be  expected  to  keep  indefinitely  insofar  as 
their  keeping  quality  depends  on  freedom  from  bacterial  action. 
Milk  powders  with  excessive  moisture  content  and  milk  powders 
that  are  exposed  to  dampness,  on  the  other  hand,  are  prone  to  be- 
come lumpy,  moldy  and  to  develop  diverse  undesirable  flavors. 

Air,  Light  and  Heat;  Relation  to  Stale  Flavor,  Tallowy  and 
Rancid  Flavor. — In  spite  of  the  fact  that  the  low  moisture  con- 
tent renders  milk  powders  practically  immune  to  bacterial  action, 
they  are  subject  to  deterioration  with  age  when  certain  other  con- 
ditions, such  as  air,  light  and  heat  are  favorable,  or  when  metals  and 
metallic  salts  are  present,  or  both,  and  experience  has  amply  dem- 
onstrated that  practically  all  milk  powders  made  from  the  usual 
quality  of  milk  under  the  present  methods  of  manufacture  and 
packing,  and  usual  conditions  incident  to  storage,  develop  a  dis- 
agreeable stale  flavor,  which  often  degenerates  into  a  tallowy  or  so- 
called  rancid  flavor  with  age. 

Exact  data  showing  the  fundamental  changes  which  these  pow- 
ders undergo  are  not  available,  but  the  findings  of  ,Rogers,  Hunziker 
and  others,1  as  the  result  of  extensive  experimental  studies  of  the 
keeping  quality  of  butter  strongly  suggest,  that  these  changes  are 
of  chemical  rather  than  of  biological  nature  and  that  oxidation  of 


Hunziker.     The  Butter  Industry,   1920. 


326         COMPOSITION  AND  PROPERTIES  OF  MII^K  POWDERS 

one  or  more  of  the  constituents  of  these  products  plays  an  important 
role.  Success  in  the  manufacture  of  milk  powders  of  superior 
keeping  quality,  therefore,  demands  also  the  protection  of  the  prod- 
uct against  agencies  that  invite  oxidation. 1 

Exclusion  of  Air. — The  oxidizing  power  of  air  is  well  known. 
Milk  powder  exposed  to  atmospheric  air  will  not  keep.  It  soon  de- 
velops a  stale  flavor,  and  if  it  contains  a  considerable  percentage  of 
butterfat  it  becomes  tallowy. 

For  this  reason  milk  powder  should  be,  and  usually  is,  packed 
in  such  a  manner  as  to  exclude  the  outside  air  as  much  as  possible. 
The  powder  packed  in  bulk  is  sealed  in  barrels  lined  with  heavy 
paper.  Smaller  packages  consist  of  tin  cans,  or  fibre  cans  with  tin 
ends  and  friction  caps. 

Unfortunately  the  body  of  the  milk  powder  itself  is  not  en- 
tirely free  from  air,  so  that  unless  packed  under  vacuum  there  al- 
ways is  some  air  in  the  package.  While  protection  against  free  ex- 
posure to  outside  air,  by  proper  packing,  greatly  minimizes  the  de- 
teriorating action,  and  does  distinctly  enhance  the  keeping  quality 
of  the  powder,  the  air  present  in  the  sealed  package  is  sufficient  to 
cause  slow  deterioration  when  other  conditions,  such  as  heat  or 
metallic  salts,  or  both,  are  present.  The  packing  of  milk  powder  in 
vacuo  would  undoubtedly  assist  in  preserving  the  milk  powder. 

Exclusion  of  Light. — 'The  rays  of  light  intensify  the  oxidiz- 
ing action  of  the  air.  It  is,  therefore,  important  that  milk  powder 
be  kept  in  the  dark.  This  is  automatically  accomplished  by  sealing 
it  in  the  usual  commercial  packages.  If  the  powder  must  be  held 
in  the  factory  for  a  considerable  number  of  hours  before  packing, 
it  should  be  kept  in  covered  containers.  Remnant  barrels,  or  other 
broken  packages  in  the  home  or  in  industrial  establishments  using 
milk  powder  should  be  kept  tightly  covered. 

Effect  of  Heat. — Heat,  similar  as  lig'ht,  intensifies  the 
oxidizing  action  of  air  and  of  other  oxidizers  and  catalizers.  Milk 
powder  kept  at  relatively  high  temperatures  becomes  stale  and  de- 
velops other  defects  quicker  than  milk  powder  kept  in  the  cold. 

Metals  and  Metallic  Salts. — Certain  metals  and  their  alloys 


1  The  sensitiveness  of  most  of  the  spray  process  milk  powders  toward 
oxidizing  agents  is  augmented  by  the  fact  the  atomizing  process  under  high 
pressure  causes  a  subdivision  of  the  fat  globules,  depriving  the  fat  of  at 
least  a  portion  of  the  protective  gelatinous  layer  which  surrounds  each  orig- 
inal fat  globule,  thereby  exposing  the  fat  more  directly  to  the  destructive 
oxidizing  agents. 


COMPOSITION  AND  PROPERTIES  OF  MILK  POWDERS         327 

and  salts  are  most  active  oxidizers.  This  is  especially  the  case  of 
copper  and  its  alloys,  such  as  brass  and  German  silver ;  also  the  salts 
of  copper.  Iron,  while  not  inert  from  the  standpoint  of  oyidation, 
is  much  less  active  and  its  salts  exert  but  a  slight  oxidizing  action. 
Tin  and  nickel  have  no  oxidizing  action. 

On  the  basis  of  these  facts  it  is  not  improbable,  that  the 
holding,  heating"  and  condensing  of  milk  in  copper  containers, 
and  the  use  of  copper  drums  in  film-drying  and  of  brass  nozzles 
in  spray-drying,  are  factors  contributory  to  the  deterioration  of 
the  resulting  milk  powders. 

Continuous,  or  flash  heaters  through  which  the  milk  passes 
rapidly  and  to  the  metal  surfaces  of  which  it  is  exposed  for  a 
very  short  time  only,  are  a  negligible  factor  in  this  respect. 
Even  if  these  surfaces  are  of  untinned  copper,  there  is  but  very 
remote  danger  of  damage  to  the  product. 

But  not  so  with  containers  in  which  the  milk  is  held  for 
hours,  or  in  which  it  is  condensed  prior  to  desiccation.  Here 
the  time  and  conditions  of  exposure  are  sufficient  to  invite 
chemical  action  of  the  acid  and  lactose  of  the  milk  on  the  copper 
surface  of  the  container.  If  the  holding  tanks  are  of  copper, 
they  should  be  heavily  tinned ;  or  in  their  place  glass  enameled 
tanks  should  be  used. 

The  copper  vacuum  pan  is  another  menace  to  keeping 
quality.  Salt's  of  copper  are  especially  likely  to  form  on  the 
inner  surface  of  the  dome  which  is  exposed  to  the  spray  and  to 
the  volatile  acids  of  the  boiling  milk.  After  each  day's  work 
the  dome,  as  well  as  all  the  other  parts  of  the  interior  of  the 
pan,  should  be  scrupulously  cleaned  to  prevent  any  accumulation 
of  copper  salts,  which  would  otherwise  become  a  part  of  the 
next  batch  and  of  the  milk  powder  made  therefrom. 

In  the  manufacture  of  whole  milk  powder,  particularly,  due 
to  the  action  of  the  copper  of  the  vacuum  pan  on  the  butterfat. 
the  tendency  to  cause  damage  to  the  finished  product,  is  great. 
It  is  advisable  to  skim  the  whole  milk,  condense  the  skim  milk 
only  and  add  the  cream  after  condensing,  in  order  to  minimize 
this  danger. 

Sandblasted  iron  pipes  are  preferable  to  so  called  sanitary 
pipes,  unless  the  inside  copper  surface  of  the  sanitary  pipes  is 
properly  tinned  and  the  tin  coating  is  reasonably  permanent. 


328         COMPOSITION  AND  PROPERTIES  OF  MILK  POWDERS 

To  what  extent  the  brass  nozzles  jeopardize  .the  keeping 
quality  of  the  powder  is  difficult  to  say.  But  it  is  well  known 
that  they  suffer  considerable  wear  as  the  result  of  the  spraying, 
and  this  means  that  the  atomized  spray  carries  off  particles  of 
brass  w'hich  later  become  a  part  of  the  finished  powder. 

The  metal  drums  used  in  the  film-drying  process  are  gen- 
erally constructed  of  metal  other  than  copper.  Many  are  of 
highly  polished  steel  and  some  are  nickel  plated.  The  desiccat- 
ing equipment  used  in  this  process  is  therefore  not  exposing  the 
product  to  copper  and  copper  salts,  thereby  largely  avoiding  the 
possibility  of  injuring  the  keeping  quality  of  the  resulting  milk 
powder  through  this  channel. 

Insects  in  Milk  Powder. — Milk  powder  may,  and  under  cer- 
tain conditions  does,  become  infested  with  insect  life,  such  as 
maggots,  weevil,  etc.  This  infection  may  take  place  in  the  fac- 
tory itself,  but  more  often  it  is  the  result  of  contamination  after  it 
leaves  the  factory. 

Such  contamination  is  generally  due  to  a  faulty  package. 
Whenever  the  seal  is  broken  the  danger  of  insect  invasion  is 
very  great.  Manufacturers  have  found  also  that  packages  sent 
to  the  tropics  are  especially  prone  to  succumb  to  this  nuisance, 
the  prevention  of  which  necessitated  the  packing  of  the  powder 
destined  for  the  tropics,  in  hermetically  sealed  cans. 

Lumpy  Milk  Powder. — As  previously  stated,  milk  powder 
exposed  to  dampness  invariably  becomes  lumpy,  and  even  when 
exposed  to  atmospheric  air  of  normal  humidity  it  will  gradually 
form  lumps,  owing  to  the  highly  hygroscopic  properties  of  the 
milk  powder.  In  order  to  prevent  lumpiness,  the  powder  must 
be  stored  in  a  dry  place  and  packed  in  a  manner  to  protect  it 
against  direct  contact  with  atmospheric  air. 

At  best  milk  powjder  has  an  inherent  tendency  to  "lump  up." 
This  is  especially  true  of  flaky  powders.  The  more  granular 
powders  yield  less  readily  to  this  defect. 

In  order  to  minimize  the  tendency  toward  lumpiness,  the 
milk  powder  should  be  allowed  to  cool,  after  desiccation  and 
before  sifting  and  packing.  If  sifted  and  packed  while  still 
warm,  the  soft  condition  of  the  fat  causes  the  particles  to  lump 
together  after  sifting.  If  sifted  and  packed  after  the  milk  powder 
has  surrendered  its  heat,  the  fat  has  had  an  opportunity  to 


COST  OF  MANUFACTURE  329 

solidify  and  harden  and  after  sifting  the  particles  remain  separate 
and  granular  and  do  not  so  readily  stick  together  in  the  form 
of  lumps. 

COST  OF  MANUFACTURE. 

The  approximate  cost  of  manufacture  of  whole  milk  powder 
and  skim  milk  powder  is  indicated  below : 

Cost  of   Whole   Milk   Powder. 

100  Ibs.  whole  milk $3.350 

Barrels  and  liners  per  100  Ibs.  milk 100 

Labor  per  100  Ibs.  milk 193 

Fuel  (condensing  and  drying)  per  100  Ibs.  milk.  .      .089 

Overhead  per  100  Ibs.  milk. .074 

Interest,  insurance,  etc.,  per  100  Ibs.  milk 050 


Total  cost  per  100  Ibs.  milk $3.856 

Total  cost  per  pound  of  whole  milk  powder, 
calculated  on  basis  of  12.5  pounds  of  powder 
made  from  100  pounds  of  whole  milk,  when 
price  of  whole  milk  is  $3.35 $0.3085 

Cost  of  Skim  Milk  Powder. 

100  Ibs.  skim  milk $1.13 

Barrels  and  liners 068 

Fuel    (condensing  and  drying)   per  100  Ibs.  skim 

milk 089 

Labor  per  100  Ibs.  skim  milk .  . 193 

Overhead  per  100  Ibs.  skim  milk 074 

Interest,  insurance,  etc.,  per  100  Ibs.  skim  milk.  .      .040 


Total  cost  per  100  Ibs.  skim  milk $1.594 

Total  cost  per  pound  of  skim  milk  powder, 
calculated  on  basis  of  8.5  pounds  powder  made 
from  100  pounds  skim  milk,  when  price  of  skim 
milk  is  $1.13 $0.1875 

MARKETS. 

The  uses  of  milk  powder  are  very  diversified.     Whole  milk 
powder  is  widely  advertised  for  infant  food  and  for  general  family 


\ 
330  DRIED  BUTTERMILK  AND  DRIED  WHEY 

use.  Considerable  quantities  are  used  by  market  milk  dealers  for 
"reconstituting"  milk  for  market  milk  purposes,  especially  at  times 
of  shortage  of  the  fluid  milk  supply.  Large  quantities  of  whole  milk 
powder  are  absorbed  also  by  chocolate  factories  in  the  manufacture 
of  milk  chocolate,  the  butterfat  being  one  of  the  essential  com- 
ponents on  which  the  milk  chocolate  depends  for  its  superior 
smoothness  and  flavor. 

Skim  milk  powder  is  used  in  the  consumer's  kitchen,  in  baker- 
ies and  confectioners'  establishments,  in  the  manufacture  of  ice 
cream,  fermented  milk  beverages,  and  starters  used  for  cream  ripen- 
ing where  milk  and  skim  milk  are  not  available ;  in  the  preparation 
of  baking  powders,  of  pure  cultures  of  lactic  acid  bacteria,  of  drugs, 
choice  toilet  soaps,  etc.  In  European  countries  the  chocolate  fac- 
tories purchase  vast  quantities  of  skim  milk  powder  in  the  manu- 
facture of  milk  chocolate  and  allied  products,  and  manufacturers  of 
diverse  prepared  food  products,  such  as  cereals,  soups,  noodles,  and 
vegetables,  furnish  additional  markets  for  this  valuable  dairy 
product. 

CHAPTER  XXVIII. 
DRIED    BUTTERMILK    AND    DRIED   WHEY. 

These  by-products  of  the  creamery  and  cheese  factory  can  be 
reduced  to  a  powder  in  a  similar  way  and  by  the  same  processes 
and  machinery  as  are  used  in  the  manufacture  of  dried  milk  and 
dried  skim  milk. 

Dried  buttermilk  makes  a  splendid  chicken  feed,  both  for  egg 
production  and  for  fattening  chickens,  and  it  is  used  also  to  make 
up  a  part  of  the  ration  for  feeding  hogs  and  young  stock.  It  is  best 
diluted  to  about  the  original  buttermilk  (one  part  powder  in  ten 
parts  water)  and  mixed  with  the  grain  feed  into  a  mush. 

Like  fresh  buttermilk,  so  is  dried  buttermilk  a  wholesome,  nu- 
tritious and  easily  digested  food  and  recommends  itself  especially  to 
persons  with  weak  digestion.  When  properly  made,  buttermilk 
powder  keeps  indefinitely  and  may,  therefore,  be  available  for  im- 
mediate use  at  all  times. 

The  following  analyses  show  the  composition  of  buttermilk 
powder  and  of  the  fresh  buttermilk  from  which  it  was  made : 


DRIED  BUTTERMILK  AND  DRIED  WHEY  331 

Composition  of  Buttermilk  Powder. 

Fresh  buttermilk         Buttermilk  powder 

Butterfat  1.17  per  cent  11.70  per  cent 

Proteids  3.00  per  cent  36.24  per  cent 

Lactose  2.97  per  cent  35.50  per  cent 

Ash  .85  per  cent  8.25  per  cent 

Acidity  .60  per  cent  6.00  per  cent 

Water  91.63  per  cent  4.32  per  cent 

Total  100.22  per  cent  102.01  per  cent 

1  The  buttermilk  of  which  the  composition  is  shown  in  the  above 
table  was  made  at  the  plant  of  the  Buffalo  Foundry  and  Machine 
Company,  Buffalo,  N.  Y.,  under  the  supervision  of  the  writer.  The 
machine  used  was  of  the  Buflovak  type.  The  buttermilk  was  fur- 
nished by  Schlosser  Bros.,  of  Frankfort,  Indiana.  This  batch  of 
buttermilk  happened  to  be  abnormally  high  in  butterf at ;  therefore 
the  large  butterfat  content  of  the  finished  product.  About  thirty 
pounds  of  steam  pressure  were  used  in  the  drying  drum,  the  tem- 
perature in  the  vacuum  chamber  was  125  degrees  F.  and  the  vacuum 
twenty-five  to  twenty-six  inches  of  the  mercury  column. 

This  buttermilk  powder  had  a  nice,  clean,  acid  taste,  it  was 
much  relished  by  all  who  sampled  it  and,  when  fed  to  chickens  for 
fattening,  produced  satisfactory  gains  in  weight. 

The  annual  production  of  buttermilk  in  the  United  States  was 
4,341,157  pounds  in  1918  and  5,278,827  pounds  in  1919. 

The  chief  obstacle  to  extensive  production  of  buttermilk  pow- 
der lies  in  the  fact  that  the  manufacturing  cost  involved  in  reducing 
buttermilk  to  dryness  is  very  high  in  proportion  to  the  market  value 
of  the  finished  product,  when  used  for  hog  and  chicken  feeding. 

Buttermilk  powder  can  be  manufactured  by  any  of  the  processes 
described  under  the  manufacture  of  milk  powder.  However  the 
spray  process  is  not  as  well  suited  for  the  desiccation  of  buttermilk 
as  is  the  film,  or  roller  process. 

In  the  spray  process  there  is  a  considerable  tendency  for  the 
milk  to  clog  the  spray  nozzles.  Again,  the  cost  of  manufacture  by 
the  spray  process  is  greater  than  that  by  the  film  process.  As 
stated  under  the  manufacture  of  milk  powder,  heat  in  the  form  of 


1  Hunziker,    Indiana   Agricultural   Experiment    Station,    Twenty-sixth   An- 
nual Report,   1913. 


332  MA^TSD  MILK 

heated  air,  is  not  as  economically  and  as  efficiently  utilized  as  heat 
in  the  form  of  steam  applied  in  steamed-heated  metal  drums. 

While,  as  previously  shown,  the  spray-drying  process  is  the  only 
process  of  desiccating  milk,  that  preserves  the  original  solubility  of 
the  milk,  this  advantage  is  lost  in  the  case  of  buttermilk.  The  acid 
in  the  buttermilk  has  changed  the  casein  from  its  fine  emulsion, 
such  as  it  represents  in  normal  milk,  to  a  condition  which  renders 
the  particles  of  casein,  or  curd,  incapable  of  permanently  remulsi- 
f ying.  The  curd  in  commercial  buttermilk  does  not  stay  in  emul- 
sion, but  settles  to  the  bottom.  Hence  nothing  is  gained  by  drying 
the  buttermilk  by  the  more  expensive  process  of  spray-drying.  The 
film  process,  which  is  the  more  economical,  is  therefore  better 
adapted  for  the  manufacture  of  buttermilk  powder  than  the  spray- 
drying  process. 

It  is  advisable  to  precondense  the  buttermilk,  before  desiccat- 
ing, at  the  ratio  of  about  2:1. 

One  gallon  of  buttermilk  yields  about  .72  pounds  of  buttermilk 
powder,  or  the  manufacture  of  one  pound  of  powder  requires 
about  1.39  gallons  of  buttermilk.  The  cost  of  manufacture  is  esti- 
mated at  about  2  cents  per  pound  of  buttermilk  powder  or  about 
1.44  cents  per  gallon  of  buttermilk. 

Whey  powder  is  manufactured  in  a  similar  manner.  Its  chief 
value  lies  in  its  usefulness  in  the  diet  of  infants  and  invalids,  with 
whom  the  consumption  of  casein  produces  digestive  disturbances. 
Since  fresh  whey  is  often  not  obtainable,  the  whey  powder,  the  good 
keeping  quality  of  which  permits  of  keeping  it  on  hand,  furnislies 
an  admirable  substitute.  When  made  from  sour  whey,  it  offers 
many  advantages  in  cooking  and  baking  and  should  be  especially 
well  suited  for  such  dishes  as  pan  cakes,  etc. 

MALTED    MILK.1 

Definition. — The  product  known  as  malted  milk  is  that  re- 
sulting from  the  combination  of  whole  milk  with  the  extract  of 
malted  barley  and  wheat  flour,  and  the  mixture  is  reduced  to  a  dry 
form  by  desiccation  in  vacuo. 

History  of  Malted  Milk  Industry. — The  process  of  the  manu- 
facture of  malted  milk  was  invented  by  Mr.  William  Horlick,  of 


1  Information  on  Definition,  History  and  Process  of  Manufacture,  received 
through  the  courtesy  of  Horlick's  Malted  Milk  Co.,  Racine,  Wis.,  March  8, 
1918. 


MAI/TED  MILK 


333 


Racine,  Wis.,  in  the  year  of  1883.  The  product  was  first  placed  on 
the  market  under  the  name  of  "Malted  Milk/'  given  it  by  its  in- 
ventor, in  1887. 

Prior  to  the  advent  of  Horlick's  malted  milk  Mr.  Horlick  was 
making  "Horlick's  Food."  It  was  through  suggestions  of  members 
of  the  medical  profession,  who  complained  that  it  was  almost  im- 
possible to  obtain  first  class,  pure,  clean,  wholesome,  whole  milk,  that 
Mr.  Horlick  took  up  the  idea  of  malted  milk.  In  consultation  with 
Dr.  R.  C.  Hindley,  then  Professor  of  Chemistry  at  the  Racine  Col- 
lege, who  later  became  Chief  Chemist  and  Superintendent  for  Mr. 
Horlick,  the  manufacture  of  malted  milk  was  subjected  to  consider- 
able experimenting  by  its  inventor  before  the  product  reached  the 
market  in  its  perfected  form. 

The  convenience,  nutri- 
tive value  and  digestibility 
of  this  product  recommended 
themselves  to  and  were  ap- 
preciated by  the  medical 
profession,  and  its  relishing 
properties  appealed  to  the 
public.  The  industry  grew 
rapidly  and  is  today  assum- 
ing large  proportions. 

Manufacture  of  Malted 
Milk. — A  mash  is  prepared 
by  mixing  wheat  flour  with 
barley  malt  of  good  diastatic 
quality.  This  mash  is  raised 
to  the  proper  temperature 
for  a  sufficient  length  of  time 
to  insure  the  complete  con- 
version of  the  insoluble 
starch  into  the  soluble  malt 
sugars  dextrin  and  maltose. 
This  conversion  is  closely 
akin  to  starch  digestion  in 
the  human  system,  hence  the 
resulting  liquid  is  essentially  a  predigested  product,  claimed  to 
be  of  much  value  as  a  special  food  for  infants  and  invalids. 


Tig.  109.     Vacuum,  pan  for  malted  milk 
Courtesy  of  Arthur  Harris  &  Co. 


334  MAI/TSD  MILK 

This  extract  is  combined  with  whole  milk  and  reduced  to  a  dry 
powder  in  a  vacuum  at  such  a  low  temperature  as  will  thoroughly 
pasteurize  the  malted  milk  and  yet  preserve  its  digestibility. 

Keeping  Quality  of  Malted  Milk. — Malted  milk  is  the  only 
milk  powder  made  from  whole  milk  that  will  keep  indefinitely  in 
any  climate.  Those  who  have  subjected  the  manufacture  of  malted 
milk  to  most  intensive  study  hold,  that  the  keeping  quality  of  malted 
milk  is  due  to  the  fact  that  the  fat  globules  are  very  finely  divided 
and  are  surrounded  by  a  coating  or  envelope  of  gluten,  sugars  and 
salts,  which  protects  the  fat  against  the  deteriorating  action  of  the 
air. 

In  dried  whole  milk  the  volume  of  fat  is  too  great  and  the  pro- 
portion of  other  solids  too  limited,  to  cause  the  fat  globules  to  be 
properly  coated,  the  air  therefore  has  more  or  less  access  to  the  fat, 
causing  such  changes  as  are  prone  to  lead  to  the  development  of  a 
tallowy  flavor  and  rancidity. 

The  use  of  wheat  flour,  while  originally  a  survival  of  "The 
Horlick's  Food,"  from  which  malted  milk  was  developed,  may  also 
be  responsible,  in  part  at  least,  for  the  keeping  quality  of  malted 
milk.  -Its  large  amount  of  gluten  may  assist  in  yielding  an  effective 
coating  for  the  protection  of  the  fat  globules.  Experiments  made 
with  flour  of  other  cereals  gave  results  that  did  not  warrant  their 
use  in  the  place  of  wheat  flour. 

Again,  it  has  been  experimentally  found  that  malted  milks  made 
by  mere  mechanical  mixing  of  the  required  ingredients,  also  become 
stale  and  rancid  rapidly,  and  that  the  only  product  that  has  perma- 
nent keeping  quality  is  that  in  the  manufacture  of  which  scientific 
use  is  made  of  the  action  of  enzymes  and  other  ferments,  etc. 

Uses  of  Malted  Milk. — Malted  milk  is  a  food  of  acknowl- 
edged high  degree  of  food  value  and  of  superior  digestibility.  Being 
a  whole  milk  food,  it  also  contains  the  indispensable  growth-promot- 
ing and  curative  properties  contained  in  whole  milk. 

It  is  placed  on  the  market  both  in  powder  and  in  tablet  form. 
Its  high  digestibility,  nutritive  value  and  health-protective  properties 
render  it  most  valuable  as  a  wholesome  food  for  infants  and  in- 
valids, and  its  compactness  and  keeping  quality  facilitate  its  trans- 
portation to  and  use  in  all  parts  of  the  globe.  Malted  milk,  there- 
fore, is  of  special  merit  for  use  in  countries  and  territories  which  are 


MALTED  MILK  335 

barred  by  their  geographical  location  and  climate  from  the  profitable 
husbandry  of  the  dairy  cow,  and  where  the  limitations  of  transpor- 
tation render  the  availability  of  fluid  milk  difficult  or  impossible. 

The  annual  output  of  malted  milk  in  the  United  States  was  15,- 
654,243  pounds  in  1918,  and  17,495,887  pounds  in  1919. 

Federal  Standards  for  Milk  Powder,  Skim  Milk  Powder  and 
Malted  Milk.1 — The  following  standards  of  dried  milk  products 
were  adopted  by  the  United  States  Department  of  Agriculture 
March  16,  1917,  and  became  effective  March  31,  1917,  as  per  Food 
Inspection  Decision  170: 

"DRIED  MILK  is  the  product  resulting  from  the  removal  of  water 
from  milk,  and  contains,  all  tolerances  being  allowed  for,  not  less 
than  twenty-six  per  cent  (26%)  of  milk  fat,  and  not  more  than  five 
per  cent  (5'%)  of  moisture. 

DRIED  SKIMMED  MILK  is  the  product  resulting  from  the  re- 
moval of  water  from  skimmed  milk  and  contains,  all  tolerances  being 
allowed  for,  not  more  than  five  per  cent  (5%)  of  moisture. 

MALTED  MILK  is  the  product  made  by  combining  whole  milk 
with  the  liquid  separated  from  a  mash  of  ground  barley  malt  and 
wheat  flour,  with  or  without  the  addition  of  sodium  chlorid,  sodium 
bicarbonate  and  potassium  bicarbonate  in  such  a  manner  as  to  secure 
the  full  enzymic  action  of  the  malt  extract,  and  by  removing  water. 
The  resulting  product  contains  not  less  than  seven  and  one-half  per 
cent  (7.5%)  of  butter  fat  and  not  more  than  three  and  one-half  per 
cent  (3.5%)  of  moisture." 

Dick  Process.2 — S.  M.  Dick  invented  and  patented  a  spray- 
drying  apparatus  for  milk,  U.  S.  patent  No.  1,298,470,  1919, 
similar  to  the  McLachlan  patent  No.  806,747.  In  the  Dick  dryer 
the  milk  enters  by  gravity  and  is  sprayed  and  distributed  by  a 
revolving  disc  arrangement.  Part  of  the  heated  air  enters  at 
the  top  and  part  at  the  bottom  of  the  desiccating  chamber..  The 
air  entering  at  the  bottom  is  hotter  than  that  entering  at  the  top. 


1  United  States  Department  of  Agriculture,  Food  Inspection  Decision  170, 
March  31,  1917. 

2  This  process   came   to   the  author's  attention   too   late  for   detailed   dis- 
cussion in  this  volume. 


PART  VII. 

STANDARDIZATION,  TESTS  AND  ANALYSES 

OF  MILK,  CONDENSED  MILK  AND 

MILK  POWDER 

CHAPTER  XXIX. 
STANDARDIZATION. 

Prior  to  the  enactment  of  the  Federal  Food  and  Drugs  Act, 
which  became  effective  January  1,  1907,  the  milk  condensing 
factories  made  no  special  effort  to  place  on  the  market  a  product 
of  any  definite  and  specific  composition.  The  milk  was  con- 
densed, either  as  whole  milk,  no  matter  what  the  original  com- 
position of  the  fluid  milk  was,  without  modification,  or  it  was 
partly  skimmed  or  wholly  skimmed,  before  condensing.  If  any 
effort  towards  modification  of  the  composition  was  made,  such 
effort  was  practically  wholly  confined  to  the  regulation  of  the 
fat  content  of  the  finished  product  and  even  in  such  cases  wide 
fluctuations  were  quite  frequent. 

With  the  enforcement  of  the  Federal  Food  and  Drugs  Act, 
the  milk  condenseries  found  themselves  called  upon  to  manu- 
facture a  product  that  would  comply  with  the  Federal  standards 
I  established  and  which  prescribed  the  minimum  per  cent  of  fat 
and  milk  solids  permissible  in  condensed  milk. 

,It  became  necessary  therefore  to  guard  against  the  produc- 
tion of  condensed  milk,  the  per  cent  fat  and  milk  solids  of  which 
fell  below  the  specified  standard.  And  later,  with  the  rapid 
development  of  the  condensed  milk  industry,  competition 
gradually  compelled  the  individual  concerns  to  not  only  avoid 
the  manufacture  of  an  illegal  product  by  causing  its  valuable 
components  to  fall  short  of  the  percentage  required  by  the 
standard,  but  to  so  modify  the  composition  as  to  not  have  the 
finished  product  materially  exceed  the  required  standard,  in 
order  to  keep  down  the  cost  of  manufacture.  Furthermore,  in 
the  case  of  bulk  condensed  milk,  which  goes  to  confectioners  and 


STANDARDIZED  CONDENSED  MII  337 


rder/ 

iza- 


ice  cream  manufacturers,  the  buyer  often  specifies  in  his  order 
the  desired  composition  of  the  product,  necessitating  standardiza 
tion  to  meet  these  special  .demands. 

These  factors  and  conditions  inevitably  led  to  the  adoption 
of  the  practice  of  carefully  standardizing  condensed  milk  for  fat 
and  milk  solids.  The  details  of  methods  used  for  standardizing 
vary  considerably  with  different  manufacturers.  The  principle 
upon  which  standardization  is  based,  however,  is  obviously  very 
much  the  same  under  all  conditions,  and  variations  in  details 
affect  the  results  largely  only  with  reference  to  the  degree  of 
accuracy. 

Some  manufacturers  standardize  the  fluid  milk  before  con- 
densing, others  prefer  to  standardize  after  evaporation  only, 
while  still  others  standardize  both,  the  fluid  milk  and  then  again 
the  finished  product  just  prior  to  canning.  Each  of  the  three 
methods  is  practical  and  the  double  method  of  standardizing 
before  and  after  condensation  is  obviously  the  most  exact.  In 
the  case  of  sweetened  condensed  milk  standardization  before 
condensation  is  preferable  inasmuch  as  the  admixture  to  the 
finished  product  of  water,  skim  milk  or  cream  is  not  advisable 
from  the  standpoint  of  keeping  quality,  unless  these  products 
have  been  previously  properly  pasteurized.  In  the  case  of 
evaporated  milk,  which  is  much  thinner,  more  miscible  and  which 
is  subsequently  sterilized,  these  objections  are  largely  removed. 

The  materials  generally  used  for  standardizing  are  skim 
milk,  condensed  skim  milk,  cream,  butter  and  water.  Water  is 
used  only  to  lower  the  per  cent  total  solids,  or  the  degree  of 
concentration,  and  is  of  service  only  after  condensation  of  the 
milk. 

The  calculations  employed  for  standardization  are  identical 
for  all  forms  of  condensed  milk  and  milk  powder,  both  sweetened 
and  unsweetened.  The  addition  of  cane  sugar  to  the  fluid  milk 
does  not  alter  the  ratio  of  fat  to  milk  solids,  since  the  added 
sugar  merely  displaces  a  portion  of  the  water  in  the  finished 
product. 

The  per  cent  total  solids  in  the  condensed  milk  is  controlled 
primarily  by  the  degree  of  concentration  as  determined  by  the 
Beaume  hydrometer  or  by  gravimetric  analysis  and  it  may  be 


338  STANDARDIZED  CONDENSED  MILK 

further  modified  by  the  addition  of  water  to  the  finished  product 
in  case  condensation  has  passed  beyond  the  desired  point. 

Aside  from  this,  the  fundamental  effort  of  standardization 
is  confined  to  securing  the  desired  proportion  of  butter  fat  to 
milk  solids  not  fat.  When  this  is  accomplished  all  that  is  neces- 
sary to  insure  the  required  composition  is  to  subject  the  product 
to  the  necessary  degree  of  concentration. 

Standardizing  the  Fluid  Milk. — In  order  to  properly  stand- 
ardize the  fluid  milk  it  is  necessary  to  know  the  required  per 
cent  fat  and  solids  not  fat  in  the  finished  product  and  the  per  cent 
fat  and  solids  not  fat  in  the  milk  to  be  standardized  and  then 
to  calculate  the  proportion  of  fat  and  solids  not  fat  needed  in 
the  fluid  milk.  This  calculation  is  most  conveniently  made  by 
allegation.  This  then  shows  the  amount  of  fat  or  solids  not 
fat,  as  the  case  may  be,  that  must  be  added  to  secure  the  desired 
proportion  of  these  ingredients  and  from  this  the  amount  of 
cream,  or  butter,  or  skim  milk  that  must  be  used  for  standard- 
izing can  be  readily  determined. 

Example  1. 

The  standard  for  evaporated  milk  is  7.8  per  cent  fat  and 
25.5  per  cent  total  solids,  or  (25.5  —  7.8)  =  17.7  per  cent  solids 
not  fat. 

Amount  fluid  milk  in  batch,  7,000  pounds. 
Fat  in  fluid  milk,  3.3  per  cent. 
Solids  not  fat  in  milk,  9.0  per  cent. 
Fat  wanted  in  evaporated  milk,  7.8  per  cent. 
Solids  not  fat  wanted  in  evaporated  milk,  17.7  per  cent. 
What  per  cent  fat  should  fluid  milk  contain? 
How  much  cream,  testing  25  per  cent  fat,  must  be  added? 
Answer:   s.  n.  f.  in  c.  m.  :  s.  n.  f.  in  r.  m.  =  f.  in  c.  m.   :  X  5 
=  X  % •  f-  required  in  r.  m. 

s.  n.  f.  =  solids  not  fat. 
f.          =  fat. 

c.  m.    —  condensed  milk, 
r.  m.    =  raw  or  fluid  milk. 
17.7  :  9.  =  7.8  :  X  ;  X  =  3.966%  fat. 

The  raw  milk  must  contain  3.966%  fat. 


STANDARDIZED  CONDENSED  MILK 


339 


How  much  25%  cream  is  required  to  raise  the  per  cent  fat 
in  the  7,000  pounds  of  milk  testing  3.3%  fat  to  3.966%  ? 

3.3     ir ^i   21.04 


3.96 


.66 


21.70 

Enough  25%  cream  must  be  added  to  the  raw  milk  so  that 
each  21.7  pounds  of  standardized  milk  contains  .66  pounds  of 
added  cream  and  21.04  pounds  of  the  original  milk.  Hence 
21.7  :  .66  =  7000  :  X  ;  X  =  213.  Ibs.  of  cream. 

Total   batch,   7000  pounds. 

25%   cream,      213  pounds. 

3.3%    milk,     6787  pounds. 

Example  2. 

Amount  of  fluid  milk  in  batch,  7,000  pounds. 
Fat  in  fluid  milk,  4.5  per  cent. 
Solids  not  fat  in  fluid  milk,  8.5  per  cent. 
Fat  wanted  in  evaporated  milk,  7.8  per  cent. 
Solids  not  fat  wanted  in  evaporated  milk,  17.7  per  cent. 
How  much  fat  should  fluid  milk  contain?    How  much  skim 
milk  must  be  added? 

Answer:  17.7  :  8.5  =  7.8  =  X  ;  X  =  3.75%.  The  fluid  milk 
must  contain  3.75%  fat. 

How  much  skim  milk  must  be  added  to  lower  the  per  cent 
fat  in  the  fluid  milk  to  3.75  ? 


4.5 


3.75 


3.75 


.75 


Enough  skim  milk  must  be  added  to  the  fluid  milk  so  that 
each   4.5   pounds   of  standardized   milk   contains   .75   pounds   of 


340 


STANDARDIZED  CONDENSED  MILK 


added    skim    milk    and    3.75    pounds    of   original    milk.      Hence 
4.50  :  .75  =  7000  :  X  ;  X  =  1167  pounds  of  skim  milk. 

Total   batch,  7000  pounds. 

Skim    milk,     1167  pounds. 

4.5 %,  milk,     5833  pounds. 

Standardization  of  Finished  Product. — In  a  similar  manner 
standardization  may  be  accomplished  after  condensation.  In 
this  case  the  proportion  of  solids  is  best  increased  or  the  propor- 
tion of  fat  reduced  by  the  addition  of  condensed  skim  milk  in 
the  place  of  ordinary  skim  milk,  while  the  proportion  of  fat  is 
increased  by  the  addition  of  cream  as  explained  under  Stand- 
ardization of  Fluid  Milk. 

If  it  is  desired  to  lower  the  total  solids  in  the  finished 
product,  without  affecting  the  proportion  of  solids  not  fat  to 
fat,  the  necessary  amount  of  water  required  is  determined  as 
follows : 

Example  3. 

Evaporated  milk  in  batch,  3000  pounds. 
Total  solids  in  evaporated  milk,  27.%. 
Total  solids  desired,  25.5%. 
How  much  water  must  be  added? 
Answer : 


27. 


0. 


25.5 


25.5 


1.5 


To  each  25.5  pounds  evaporated  milk  must  be  added  1.5 
pounds  water.  Hence  25.5  :  1.5  =  3000  :  X  ;  X  =  176.5  pounds 
of  water. 

Original   batch  evaporated  milk,  3000      pounds. 

Water  added,  176.5  pounds. 

Standardized  evaporated  milk,       3176.5  pounds. 

The  results  of  standardization  in  which  cream  is  used  to 
alter  the  proportion  of  fat  to  solids  not  fat,  are  not  absolutely 
mathematically  accurate,  because  of  the  fact  that  the  per  cent 


STANDARDIZED  CONDENSED  MILK  341 

of  solids  not  fat  in  the  cream  is  somewhat  lower  than  in  milk. 
This  causes  a  slight  shortage  of  solids  not  fat  in  the  standard- 
ized product.  This  error  is  so  slight,  however,  that  it  may  be 
considered  within  the  limits  of  the  experimental  error  and  for 
all  practical  purposes  this  method  of  standardization  may  be 
accepted  as  reliable  and  accurate. 

Standardization  of  Sugar  (Sucrose)  in  Sweetened  Condensed 
Milk. — This  is  most  readily  accomplished  by  standardizing 
the  proportion  of  sugar  to  the  per  cent  total  solids  in  the  fresh 
milk. 

If  it  is  desired  to  secure  a  sweetened  condensed  milk,  the  milk 
solids  of  which  merely  comply  with  the  Federal  standard  of  28  per 
cent,  it  is  desirable  and  necessary,  from  the  standpoint  of  keeping 
quality,  to  add  enough  sugar  (sucrose)  so  as  to  have  the  finished 
product  contain  at  least  44  per  cent  sucrose. 

Example  4. 

Amount  of  fluid  milk  in  batch,  15,000  pounds. 

Fluid  milk  contains  12  per  cent  total  solids. 

How  much  sugar  must  be  added  in  order  to  insure  the  sweet- 
ened condensed  milk  to  contain  44  per  cent  sucrose,  when  the  milk 
has  been  condensed  sufficiently  to  contain  28  per  cent  milk  solids  ? 

Answer  :     28  :  44  =  12  :  X  :  X  =  18.87. 

To  every  100  pounds  of  fluid  must  be  added  18.87  pounds 
sucrose. 

To  15,000  pounds  fluid  milk  must  be  added 

18.87  X  15,000 

=  2830. D  pounds  sucrose. 

100 

If  it  is  desired  to  produce  a  sweetened  condensed  of  heavy 
body  and  containing  a  high  per  cent  of  milk  solids,  as  for  instance, 
32  per  cent  milk  solids,  the  per  cent  sugar  contained  in  the  finished 
product  may  be  considerably  reduced.  Such  sweetened  condensed 
milk  may  contain,  say  40  per  cent  sucrose. 

Example  5. 

Amount  of  fluid  milk  in  batch  is  15,000  pounds. 

Fluid  milk  contains  12  per  cent  total  solids. 

How  much  sugar  must  be  added  to  insure  the  sweetened  con- 


342  CHEMICAL  TESTS  AND  ANALYSES 

densed  milk  to  contain  40  per  cent  sucrose  when  the  milk  has  been 
condensed  sufficiently  to  contain  32  per  cent  milk  solids? 

Answer :     32  :  40  =  12  :  X  :  X  =  15. 

To  every  100  pounds  of  fluid  milk  must  be  added  15  pounds 
of  sugar. 

To  15,000  pounds  fluid  milk  must  be  added 

15  X  15,000       „_ 
—  =  2250  pounds  of  sucrose. 

CHAPTER  XXX. 

CHEMICAL  TESTS  AND  ANALYSES  OF  MILK,  SWEET- 
ENED CONDENSED  MILK,  EVAPORATED  MILK 
AND  MILK  POWDERS. 

In  assembling  these  methods  of  analyses,  preference  has 
been  given  the  "Official  and  Provisional  Methods  of  Analysis," 
published  by  the  American  Association  of  Official  Agricultural 
Chemists.1  The  official  methods  have  been  modified  and  supple- 
mented by  other  methods  in  numerous  cases  wherever,  in  the 
judgment  of  the  writer  and  others,  such  modifications  and  sub- 
stitutions are  better  adapted  for  analysis  of  these  special  prod- 
ucts. A  special  effort  has  further  been  made  to  include  in  this 
chapter  modifications  and  abbreviations  of  tests  and  analyses, 
adapted  for  the  use  of  the  factory  operator,  whose  knowledge, 
skill,  facilities  and  time  are  too  limited  to  enable  him  to  success- 
fully follow  the  directions  of  the  official  methods,  or  to  execute 
delicate  and  difficult  chemical  analyses. 

For  practical  factory  tests  of  fresh  milk  on  the  receiving 
platform,  determining  its  fitness  for  condensing,  the  reader  is 
referred  to  Chapter  III,  "Inspection  of  Milk  at  the  Condensery." 

MILK. 

Specific  Gravity. 

Aerometric  Method  by  Means  of  the  Quevenne  Lactometer. 
—Use  an  accurate  Quevenne  lactometer  with  thermometer  at- 
tachment and  a  lactometer  cylinder  about  ten  inches  high  and 

1  United  States  Department  of  Agriculture,  Bureau  of  Chemistry,  Bulletin 
No.  107,  1912.  Also  Journal  of  the  Assn.  of  Official  Agr.  Chemists,  Vol.  II, 
No.  3,  Nov.  15,  1916. 


CHEMICAL  TESTS  AND  ANALYSES  343 

one  and  one-half  inches  wide.  Fill  the  cylinder  with  milk  at  a 
temperature  between  55  and  65  degrees  F.  Insert  the  lactometer 
and  when  it  has  found  its  equilibrium,  note  the  point  on  the  scale 
at  the  surface  of  the  milk.  The  correct  temperature  is  60  degrees 
F.  For  every  degree  Fahrenheit  above  60  add  one-tenth  point 
to  the  observed  reading,  and  for  every  degree  Fahrenheit  below 
60  deduct  one-tenth  point  from  the  observed  reading.  This  rule 
holds  good  only  when  the  range  of  temperature  is  within  the 
limits  of  55  degrees  and  65  degrees  F. 

The  specific  gravity  is  calculated  by  adding  1,000  to  the 
lactometer  reading  and  dividing  the  sum  by  1,000.  Example: 
Lactometer  reading  is  31  at  65  degrees  F.  Corrected  reading  is 
31.5; 

.-  .     31.5  +  1000          1A71- 

specific  gravity  is—  -  =:  1.0315, 


Gravimetric  Determination.  —  This  consists  of  the  filling  of 
a  perfectly  dry  picnometer  or  other  graduated  flask  of  known  meas- 
ure with  milk  at  the  standard  temperature  (60  degrees  F.,  or  15.5 
degrees  C.)  and  weighing  the  flask  and  contents.  The  weight  of 
the  flask  is  then  deducted  from  the  weight  of  the  flask  plus  con- 
tents and  the  difference  is  divided  by  the  weight  of  an  equal  volume 
of  water  at  standard  temperature.  The  result  is  the  specific  gravity 
of  the  milk. 

The  Westphal  balance  method  furnishes  another  accurate  means 
of  determining  the  specific  gravity.  Both  the  gravimetric  method 
and  the  Westphal  balance  method,  while  accurate  when  operated 
by  the  skillful  chemist,  require  considerable  time.  Experimental 
comparisons  have  demonstrated  that  for  all  practical  purposes  the 
Quevenne  hydrometer,  when  accurately  graduated,  yields  correct 
results,  and  the  simplicity  and  rapidity  of  its  operation  render  its 
use  in  the  determination  of  the  specific  gravity  of  milk  highly  ad- 
vantageous and  satisfactory. 

Total  Solids. 

By  Means  of  the  Babcock  Formula.  —  For  rapid  and  reason- 
ably accurate  work  the  total  solids  of  milk  may  be  determined  by 
the  use  of  the  Babcock  formula,  which  is  as  follows  : 

Total  solids  =--+  1.2  X  f. 


344  CHEMICAL  TESTS  AND  ANALYSES 

L  =  Quevenne  lactometer  reading, 
f  =.  per  cent  of  fat. 
Example :    Lactometer  reading  is  32 ;  per  cent  fat  is  4. 

Total  solids  =  -¥-+  1.2  X  4  =  12.8  per  cent. 

Gravimetric  Method.— "Heat  from  three  to  five  grams  of 
milk  at  the  temperature  of  boiling  water  until  it  ceases  to  lose 
weight,  using  a  tared  flat  dish  of  not  less  than  5  c.c.  diameter.  If 
desired,  from  fifteen  to  twenty  grams  of  pure,  dry  sand  may  be 
previously  placed  in  the  dish.  Cool  in  a  desiccator  and  weigh  rapid- 
ly to  avoid  absorption  of  hygroscopic  moisture." 

Ash. 

"Weigh  about  twenty  grams  of  milk  in  a  weighed  dish,  add 
6  c.c.  of  nitric  acid,  evaporate  to  dryness  and  ignite  at  a  tempera- 
ture just  below  redness  until  the  ash  is  free  from  carbon." 

Total  Nitrogen. 

Place  about  five  grams  of  milk  in  a  Kjeldahl  digestion  flask 
and  proceed,  without  evaporation,  as  described  under  "Gunning 
Method"  for  the  determination  of  nitrogen.  Multiply  the  percent- 
age of  nitrogen  by  6.38  to  obtain  nitrogen  compounds. 

Gunning  Method. 
Apparatus. 

(a)  Kjeldahl   flasks   for  both   digestion  and   distillation. — 
These  are  flasks  having  a  total  capacity  of  about  550  c.c.,  made  of 
hard,  moderately  thick  and  well-annealed  glass.     When  used  for 
distillation  the  flasks  are  fitted  with  rubber  stoppers  and  bulb  tubes, 
as  given  under  distillation  flasks. 

(b)  Kjeldahl  digestion  flasks. — These  are  pear-shape,  round- 
bottomed   flasks,   made   of   hard,   moderately   thick,   well-annealed 
glass,  having  a  total  capacity  of  about  250  c.c.     They  are  22  c.m. 
long  and  have  a  maximum  diameter  of  6  c.m.,  tapering  gradually  to 
a  long  neck,  which  is  2  c.m.  in -diameter  at  the  narrowest  part  and' 
flared  a  little  at  the  edge. 

(c)  Distillation  flasks. — For  distillation  a  flask  of  ordinary 
shape,  of  about  550  c.c.  capacity  may  be  used.     It  is  fitted  with  a 


CHSMICAI,  TSSTS  AND  ANALYSES  345 

rubber  stopper  and  with  a  bulb  tube  above  to  prevent  the  possibility 
of  sodium  hydrate  being  carried  over  mechanically  during  distilla- 
tion. The  bulbs  may  be  about  3  c.m.  in  diameter,  the  tubes  being 
of  the  same  diameter  as  the  condenser  and  cut  off  obliquely  at  the 
lower  end,  which  is  fastened  to  the  condenser  by  a  rubber  tube." 

Preparation  of   Reagents. 

"(a)  Potassium  sulphate. — This  reagent  should  be  pulver- 
ized before  using. 

(b)  Sulphuric   acid. — The    sulphuric    acid    should     have   a 
specific  gravity  of  1.84.     It  should  be  C.  P.,  containing  no  nitrates 
nor  ammonium  sulphate. 

(c)  Sulphuric  acid. — N-10  solution. 

(d)  Standard  alkali  solution. — The  strength  of  this  solution 
relative  to  the  acid  must  be  accurately  determined,  N-10  solution. 

(e)  Metallic  mercury  or  mercuric  oxid. — If  mercuric  oxid  is 
used  it  should  be  prepared  in  the  wet  way,  but  not  from  mercuric 
nitrate. 

(f)  Granulated  zinc  or  pumice  stone. — One  of  these  reagents 
is  added  to  the  contents  of  the  distillation  flasks,  when  found  nec- 
essary, in  order  to  prevent  bumping. 

(g)  Potassium  sulphid  solution. — A  soluti'on  of  forty  grams 
of  commercial  potassium  sulphid  in  one  liter  of  water. 

(h)  Sodium  hydroxid  solution. — A  saturated  solution  of  so- 
dium hydroxid  free  from  nitrates. 

(i)  Indicator. — A  solution  of  cochineal  is  prepared  by  digest- 
ing and  frequently  agitating  three  grams  of  pulverized  cochineal  in 
a  mixture  of  50  c.c.  of  strong  alcohol  and  200  c.c.  of  distilled  water 
for  a  day  or  two  at  ordinary  temperatures.  The  filtered  solution  is 
employed  as  indicator." 

Determination. 

Place  the  substance  to  be  analyzed  in  a  digestion  flask,  employ- 
ing from  0.7  to  3.5  grams,  according  to  its  proportion  of  nitrogen. 
Add  10  grams  of  powdered  potassium  sulphate  and  from  15  to  25 
c.c.  (ordinarily  about  20  c.c.)  of  sulphuric  acid.  Conduct  the  di- 
gestion by  starting  with  a  temperature  below  boiling  point  and 


346  CHEMICAL,  TESTS  AND  ANALYSES 

increasing  the  heat  gradually  until  frothing  ceases.  Digest  for  a 
time  after  the  mixture  is  colorless,  or  nearly  so,  or  until  oxidation 
is  complete.  Do  not  add  either  potassium  permanganate  or 
potassium  sulphid.  Dilute,  neutralize,  distil  and  titrate  with  stand- 
ard alkali.  In  neutralizing,  it  is  convenient  to  add  a  few  drops 
of  phenolphthalein  indicator,  by  which  one  can  tell,  when  the  acid 
is  completely  neutralized,  remembering  that  the  pink  color,  which 
indicates  an  alkaline  reaction,  is  destroyed  by  a  considerable  excess 
of  strong  fixed  alkali. 

•  .  . 

Casein  and  Albumin. 

"(a)  Casein. — The  determination  should  be  made  when  the 
milk  is  fresh,  or  nearly  so.  When  it  is  not  practicable  to  make  this 
determination  within  twenty-four  hours,  add  one  part  of  formal- 
dehyde to  twenty-five  hundred  parts  of  milk  and  keep  in  a  cool 
place.  Place  about  10  grams  of  milk  in  a  beaker  with  about  90  c.c. 
of  water  at  40  degrees  to  42  degrees  C.,  and  add  at  once  1.5  c.c.  of 
a  10  per  cent  acetic  acid  solution.  Stir  with  a  glass  rod  and  let 
stand  from  three  to  five  minutes  longer.  Then  decant  or  filter,  wash 
two  or  three  times  with  cold  water  by  decantation  and  transfer  pre- 
cipitate completely  to  filter.  Wash  once  or  twice  on  filter.  The 
filtrate  should  be  clear,  or  nearly  so.  If  it  be  not  clear  when  it  first 
runs  through,  it  can  generally  be  made  so  by  two  or  three  repeated 
filtrations,  after  which  the  washing  of  the  precipitate  can  be  com- 
pleted. Determine  nitrogen  in  the  washed  precipitate  and  filter  by 
the  Gunning  method.  To  calculate  the  equivalent  amount  of  casein 
from  the  nitrogen  multiply  by  6.38. 

In  working  with  milk  which  has  been  kept  with  preservatives, 
the  acetic  acid  should  be  added  in  small  proportions,  a  few  drops 
at  a  time,  with  stirring,  and  the  addition  continued  until  the  liquid 
above  the  precipitate  becomes  clear  or  very  nearly  so. 

(b)  Albumin. — Exactly  neutralize  with  caustic  alkali  the  fil- 
trate obtained  in  the  preceding  operation  (a),  add  0.3  c.c.  of  a  10 
per  cent  solution  of  acetic  acid  and  heat  the  liquid  to  the  tempera- 
ture of  boiling  water  until  the  albumin  is  completely  precipitated, 
collect  the  precipitate  on  a  filter,  wash  and  determine  the  nitrogen 
therein.  Nitrogen  multiplied  by  6.38  equals  albumin,"  or 


CHEMICAL  TESTS  AND  ANALYSES  347 

To  the  filtrate  of  the  casein  determination  add  0.3  c.c.  of  10  per 
cent  acetic  acid,  boil  until  the  albumin  is  completely  precipitated  and 
proceed  as  directed  in  previous  paragraph. 

In  the  place  of  the  above  methods  the  per  cent  of  albumin  may 
be  determined  by  subtracting  the  per  cent  of  casein  from  the  per 
cent  of  total  nitrogen. 

Milk  Sugar  (Lactose). 

Optical  Method. 
Preparation  of  Reagents. 

"(a)  Acid  mercuric  nitrate. — Dissolve  mercury  in  double  its 
weight  of  nitric  acid,  specific  gravity  1.42,  and  dilute  with  an  equal 
volume  of  water.  One  cubic  centimeter  of  this  reagent  is  sufficient 
for  the  quantities  of  milk  mentioned  below.  Larger  quantities  may 
be  used  without  affecting  the  results  of  polarization. 

(b)  Mercuric  iodid  with  acetic  acid. — Mix  33.2  grams  of  po- 
tassium iodid,  13.5  grams  of  mercuric  chlorid,  20  c.c.  of  glacial 
acetic  acid  and  640  c.c.  of  water." 

Determine  the  specific  gravity  of  the  milk  by  means  of  a  deli- 
cate hydrometer,  or,  if  preferred,  a  pycnometer.  The  quantity  of 
sample  to  be  taken  for  the  determination  varies  with,  the  specific 
gravity  and  is  to  be  measured  at  the  same  temperature  at  which  the 
specific  gravity  is  taken.  The  volume  to  be  measured  is  indicated 
in  the  following  table,  which  is  based  upon  twice  the  normal  weight 
of  lactose  (32.9  grams  per  100  metric  c.c.)  for  the  Ventzke  sugar 
scale. 

Place  the  quantity  of  milk  indicated  in  the  table  in  a  flask 
graduated  at  102.6  c.c.,  add  1  c.c.  of  the  acid  mercuric  nitrate  solu- 
tion or  30  c.c.  of  the'  mercuric  iodid  solution  (an  excess  of  these  re- 
agents does  no  harm),  fill  to  the  mark,  shake,  filter  through  a  dry 
filter  and  polarize.  It  is  not  necessary  to  heat  before  polarizing.  If 
a  200  m.m  tube  is  used,  divide  the  polariscope  reading  by  2(  or,  if  a 
400  m.m.  tube  is  used,  by  4)  to  obtain  the  per  cent  of  lactose  in  the 
sample. 


348 


CHEMICAL  TESTS  AND  ANALYSIS 


Volume   of   Milk   Corresponding  to   a   Lactose   Double   Normal 

Weight. 


Volume  of  Milk 

Volume  of  Milk 

Specific  Gravity 
of  Milk 

for  a  Lactose 
Double  Normal 
Weight  Ventzke 

Specific  Gravity 
of  Milk 

for  a  Lactose 
Double  Normal 
Weight  Ventzke 

Scale 

Scale 

c.c. 

C.C. 

1.024 

64.25 

1.031 

63.80 

1.025 

64.20 

1.032 

63.75 

1.026 

64.15 

1.033 

63.70 

1.027 

64.05 

1.034 

63.65 

1.028 

64.00 

1.029 

63.95 

1.035 

63.55 

1.030 

63.90 

1.036 

63.50 

Low's  Volumetric  Method  Modified. 
Preparation  of  Reagents. 

"(a)    Copper  sulphate  solution. — Dissolve  34.639  grams  of 
CuSO4  .5H2O  in  water  and  dilute  to  500  c.c. 

(b)  Alkaline  tartrate  solution. — Dissolve  173  grams  of  Ro- 
chelle  salts  and  50  grams  of  sodium  hydroxid  in  water  and  dilute 
to  500  c.c.   • 

(c)  Mixed  solution. — Mix  equal  volumes  of  solutions  (a)  and 
(b)  immediately  before  use. 

(d)  Standardization  of  the  thiosulphate  solution. — Prepare  a 
solution  of  sodium  thiosulphate,  dissolving  24.659  grams  of  pure 
crystals  to  1,000  c.c.     Weigh  6.36  grams  copper  foil.     Dissolve  by 
warming  in  minimum  amount  of  nitric  acid  and  water  required. 
Boil  to  expel  the  red  fumes,  add  160  c.c.  strong  bromine  water  and 
boil  until  the  bromine  is  thoroughly  expelled.     Remove  from  the 
heat  and  add  a  slight  excess  of  strong  ammonium  hydroxid ;  223  c.c. 
is  about  the  right  amount.    Again  boil  until  the  excess  of  ammonia1 
is  expelled,  as  shown  by  a  change  of  color  of  the  liquid,  and  partial 
precipitation.     Now  add  a  slight  excess  of  strong  acetic  acid  (100 
to  130  c.c.  of  80  per  cent  acid)  and  boil    for   a    minute.     Cool   to 
room  temperature  and  dilute  to  1,000  c.c.    Titrate  a  known  amount 
(10  to  15  c.c.)  of  the  copper  solution,  to  which  10  c.c.  of  a  25  per 
cent  solution  of  pure  potassium  iodid  has  been    added,    with    the 


CHEMICAL  TESTS  AND  ANALYSES  349 

thiosulphate  solution  until  the  brown  tinge  has  become  weak,  then 
add  sufficient  starch  liquor  to  produce  a  marked  blue  coloration. 
Continue  the  titration  cautiously  until  the  color  due  to  free  iodin 
has  entirely  vanished.  The  blue  color  changes  toward  the  end  to 
a  faint  lilac.  If  at  this  point  the  thiosulphate  be  added  drop  by  drop 
and  a  little  time  be  allowed  for  complete  reaction  after  each  addition, 
there  is  no  difficulty  in  determining  the  end  point  within  a  single 
drop.  One  cubic  centimeter  of  the  thiosulphate  solution  will  be 
found  to  correspond  to  .00636  grams  of  copper." 

Determination  of  Copper. 

"After  washing  the  precipitated  cuprous  oxid,  cover  the  gooch 
with  a  watch  glass  and  dissolve  the  oxid  by  means  of  5  c.c.  of  warm 
nitric  acid  (1 :1)  poured  under  the  watch  glass  with  a  pipette.  Catch 
the  filtrate  in  a  flask  of  250  c.c.  capacity,  wash  watch  glass  and 
gooch  free  of  copper ;  50  c.c.  of  Water  will  be  sufficient.  Boil  to 
expel  red  fumes,  add  5  c.c.  of  bromine  water,  boil  off  the  bromine 
and  proceed  exactly  as  in  standardizing  the  thiosulphate." 

Determination  of  Lactose. 

Place  50  c.c.  of  the  mixed  copper  reagent  in  a  beaker  and  heat 
to  the  boiling  point.  While  boiling  briskly  add  100  c.c.  of  the  lactose 
solution  containing  not  more  than  0.300  grams  of  lactose  and  boil 
for  six  minutes.  Filter  immediately  through  asbestos  and  wash. 
Obtain  the  weight  of  lactose  equivalent  to  the  weight  of  copper 
found  from  the  following  table: 


350 


CHEMICAL  TESTS  AND  ANALYSES 


"Table  for  the  Determination  of  Lactose  (Soxhlet-Wein)." 


Milli- 
grams 
of 
copper 

Milli- 
grams 
of 
lactose 

Milli- 
grams 
of 
copper 

Milli- 
grams 
of 
hte&M 

Milli- 
grams 
of 
copper 

Milli- 
grams 
of 
lactose 

Milli- 
grams 
of 
copper 

Milli- 
grams 
of 
lactose 

Milli- 
grams 
of 
copper 

Milli- 
grams 
of 
lactose 

100 

71.6 

160 

116.4 

220 

161.9 

280 

208.3 

340 

255.7 

101 

72.4 

161 

117.1 

221 

162.7 

281 

209.1 

341 

256.6 

102 

73.1 

162 

117.9 

221 

163.4 

282 

209.9 

342 

257.4 

103 

73.8 

163 

118.6 

223 

164.2 

283 

210.7 

343 

258.2 

104 

74.6 

164 

119.4 

224 

164.9 

284 

211.5 

344 

259.0 

105 

75.3 

165 

120.2 

225 

165.7 

285 

212.3 

345 

259.8 

106 

76.1 

166 

120.9 

226 

166.4 

286 

213.1 

346 

260.6 

107 

76.8 

167 

121.7 

227 

167.2 

287 

213.9 

347 

261.4 

108 

77.6 

168 

122.4 

228 

167.9 

288 

214.7 

348 

262.3 

109 

78.3 

169 

123.2 

229 

168.6 

289 

215.5 

349 

263.1 

110 

79.0 

170 

123.9 

230 

169.4 

290 

216.3 

350 

233.9 

111 

79.8 

171 

124.7 

231 

170.1 

291 

217.1 

351 

264.7 

112 

80.5 

172 

125.5 

232 

170.9 

292 

217.9 

352 

265.5 

113 

81.3 

173 

126.2 

233 

171.6 

293 

218.7 

353 

263.3 

1H 

82.0 

174 

127.0 

234 

172.4 

294 

219.5 

354 

267.2 

115 

82.7 

175 

'127.8 

285 

173.1 

295 

220.3 

355 

268.0 

116 

83.5 

176 

128.5 

236 

173.9 

296 

221.1 

356 

268.8 

117 

84.2 

177 

129.3 

237 

174.6 

297 

221.9 

35r 

239.6 

118 

85.0 

178 

130.1 

238 

175.4 

298 

222.7 

358 

270.4 

119 

85.7 

179 

130.8 

239 

176.2 

299 

223.5 

359 

271.2 

120 

86.4 

180 

131.6 

240 

176.9 

300 

224.4 

350 

272.1 

121 

87.2 

181 

132.4 

241 

177.7 

301 

225.2 

361 

272.9 

122 

87.9 

182 

m.i 

242 

178.5 

302 

225.9 

362 

273.7 

123 

88.7 

183 

133.9 

243 

179.3 

303 

226.7 

363 

274.5 

124 

89.4 

184 

134.7 

244 

180.1 

304 

227.5 

364 

275.3 

125 

90.1 

185 

135.4 

245 

180.8 

305 

228.3 

365 

276.2 

126 

90.9 

186 

136.2 

246 

181.6 

306 

229.1 

366 

277.1 

127 

91.6 

187 

137.0 

247 

182.4    , 

307 

229.8 

367 

277.9 

128 

92.4 

188 

137.7 

248 

183.2 

308 

230.6 

368 

278.8 

129 

93.1 

189 

138.5 

249 

184.0 

309 

231.4 

369 

279.6 

130 

93.8 

190 

139.3 

250 

184.8 

310 

232.2 

370 

280.5 

131 

-  94.6 

191 

140.0 

251 

185.5 

311 

232.9 

371 

281.4 

132 

95.3 

192 

140.8 

252 

186.3 

312 

233.7 

372 

282.2 

133 

96.1 

193 

141.6 

253 

187.1 

313 

234.5 

373 

283.1 

134 

96.9 

194 

142.3 

254 

187.9 

314 

235.3 

374 

283.9 

135 

97.6 

195 

143.1 

255 

188.7 

315 

236.1 

375 

284.8 

136 

98.3 

196 

143.9 

256 

189.4 

316 

236.8 

376 

285.7 

137 

99.1 

197 

144.6 

257 

190.2 

317 

237.6 

377 

286.5 

138 

99.8 

198 

145.4 

258 

191.0 

318 

238.4 

378 

287.4 

139 

100.5 

199 

146.2 

259 

191.8 

319 

239.2 

379 

288.2 

140 

101.3 

200 

146.9 

260 

192.5 

320 

240.0 

380 

289.1 

141 

102.0 

201 

147.7 

261 

193.3 

321 

240.7 

381 

239.9 

142 

102.  a 

202 

148.5 

262 

194.1 

322 

241.5 

382 

290.8 

143 

103.5 

203 

149.2 

263 

194.9 

323 

242.3 

383 

291.7 

144 

104.3 

204 

150.0 

264 

195.7 

324 

243.1 

384 

292.5 

145 

105.1 

205 

150.7 

265 

196.4 

325 

243.9 

385 

293.4 

146 

105.8 

206 

151.5 

266 

197.2 

326 

244.6 

386 

294.2 

147 

106.6 

207 

152.2 

267 

198.0 

327 

245.4 

387 

295.1 

148 

107.3 

208 

153.0 

•268 

198.8 

328 

246.2 

388 

296.0 

149 

108.1 

209 

153.7 

269 

199.5 

329 

247.0 

889 

296.8 

150 

108.8 

210 

154.5 

270 

200.3 

330 

247.7 

390 

237.7 

151 

109.6 

211 

155.2 

271 

201.1 

331 

248.5 

391 

298.5 

152 

110.3 

212 

156.0 

272 

201.9 

332 

249.2 

392 

299.4 

153 

111.1 

213 

156.7 

273 

202.7 

333 

250.0 

393 

300.3 

154 

111.9 

21,4 

157.5 

274 

203.5 

334 

250.8 

394 

331.1 

155 

112.6 

215 

158.2 

275 

204.3 

335 

251.6 

395 

302.0 

156 

113.4 

216 

159.0 

276 

205.1 

336 

252.5 

396 

302.8 

157 

114.1 

217 

159.7 

277 

205.9 

337 

253.3 

397 

308.7 

158 

114.9 

218 

160.4 

278 

206.7 

338 

254.1 

398 

304.6 

159 

115.6 

219 

161.2 

279 

207.5 

339 

254.9 

399 

305.4 

400 

306.3 

CHEMICAL  TESTS  AND  ANALYSES 


351 


Butter  Fat. 

The  Babcock  Test. 

Standard  Glassware.1 

(a)  Standard  milk  test  bottles,  graduated  to  8  per  cent  and 
with  sub-divisions  of  .1  per  cent. 

(b)  Standard  pipette  graduated  to   17.6  c.c. 

(c)  Acid  measure  graduated  to  17.5  c.c. 

(d)  Centrifuge-Babcock  tester. 

(e)  Water  bath  for  reading  at  130  to  140  degrees  F. 

(f)  Calipers  for  measuring  fat  column. 

(g)  Sulphuric  acid,  specific  gravity  1.82  to  1.83. 

Determination. 

Pipette  17.6  c.c.  of  the  properly  mixed  sample  of  milk  into 
the  milk  test  bottle.  Add  17.5  c.c.  of  acid  and  shake  until  all  the 
curd  is  completely  dissolved. 
Both  milk  and  acid  should  have 
a  temperature  of  55  to  70  de- 
grees F.  If  milk  and  acid  are 
too  warm,  set  the  sample  bot- 
tles and  the  acid  jar  into  a 
trough  or  tub  of  water  at  55  to 
70  degrees  F.  for  thirty  minutes 
before  testing.  The  test  bottles 
containing  the  mixture  of  milk 
and  acid  are  then  whirled  in 
the  Babcock  tester  for  five 
minutes  at  about  one  thousand 
revolutions  per  minute,  in  the 
case  of  a  tester  with  a  twelve- 


rig-.  110.     Babcock  tester 

Courtesy  of  Creamery  Package  Mfg. 
Company 


inch  diameter  wheel.     Fill  the 

test  bottles   to   the   bottom   of 

the  neck  with  hot  water.     The 

water   should   be   soft,   preferably    rain   water   or   distilled   water. 

If  hard  tap  water  is  used  it  should  be  boiled  to  precipitate  the 

carbonates,  otherwise  the  test  may  be  difficult  to  read,  owing  to 

the  presence  of  bubbles  of  gas  on  top  of  the  fat  column.    Revolve 


1914. 


1  Hunziker,  Indiana  Agricultural  Experiment  Station,  Circulars  41  and  42, 


352  CHEMICAL  TESTS  AND  ANALYSES 

again  at  full  speed  for  two  minutes,  fill  the  test  bottles  to  near 
the  top  of  the  graduation  with  hot  water.  Whirl  in  the  centrifuge 
for  one  minute.  Now  set  the  test  bottles  in  the  water  bath  at 
135  degrees  F.  for  five  minutes.  The  test  is  now  ready  to  be 
read.  The  figures  on  the  test  bottles  represent  per  cent.  In  the 
case  of  the  8  per  cent  standard  milk  test  bottle  the  sub-divisions 
represent  tenths  per  cent.  Read  from  the  bottom  of  the  lower 
curve  to  the  top  of  upper  curve  of  the  fat  column,  including  the 
meniscus  in  the  reading. 

Gravimetric    Method — Paper    Coil. 

"Make  coils  of  thick  filter  paper,  cut  into  strips  6.25  by  62.5 
c.m.,  and  thoroughly  extract  with  ether  and  alcohol,  or  correct 
the  weight  of  the  extract  by  a  constant  obtained  for  the  paper. 
From  a  weighing  bottle  or  weighing  pipette,  transfer  about  5 
grams  of  milk  to  the  coil,  care  being  taken  to  keep  the  end  of 
the  coil  held  in  the  fingers,  dry.  Dry  the  coil,  dry  end  down,  on 
a  piece  of  glass  at  the  temperature  of  boiling  water;  transfer  to 
an  extraction  apparatus  and  extract  with  absolute  ether  or  pe- 
troleum ether  boiling  at  about  45  degrees  C. ;  dry  the  extracted 
fat  and  weigh." 

Roese-Gottlieb  Method. 

"  Weigh  10-11  grams  of  the  milk  into  a  Rohrig  tube  or  some 
similar  apparatus,  add  1.25  c.c.  of  concentrated  ammonium  hy- 
droxid  (2  c.c.  if  the  sample  is  sour)  and  mix  thoroughly.  Add 
10  c.c.  of  95  per  cent  alcohol  by  volume  and  mix  well.  Then  add 
25  c.c.  of  washed  ether  and  shake  vigorously  for  thirty  seconds, 
then  25  c.c.  of  petroleum  ether  (redistilled  slowly  at  a  tempera- 
ture below  60  degrees  C.)  and  shake  again  for  thirty  seconds. 
Let  stand  twenty  minutes,  or  until  the  upper  liquid  is  practically 
clear.  Draw  of?  as  much  as  possible  of  the  ether-fat  solution 
(usually  0.5-0.8  c.c.  will  be  left)  into  a  weighed  flask  through  a 
small  quick-acting  filter.  The  flask  should  always  be  weighed 
with  a  similar  one  as  a  counterpoise.  Re-extract  the  liquid  re- 
maining in  the  tube,  this  time  with  only  15  c.c.  of  each  ether, 
shake  vigorously  thirty  seconds  with  each  and  allow  to  settle. 
Draw  off  the  clear  solution  through  the  small  filter  into  the  same 
flask  as  before  and  wash  the  tip  of  spigot,  the  funnel  and  the 
filter  with  a  few  c.c.  of  a  mixture  of  the  two  ethers  in  equal  parts. 


CHEMICAL  TESTS  AND  ANALYSES  353 

For  absolutely  exact  results  the  re-extraction  must  be  repeated. 
This  third  extraction  yields  usually  not  more  than  about  1  mg. 
of  fat  (about  0.02  per  cent  on  a  4  gram  charge)  if  the  previous 
ether-fat  solutions  have  been  drawn  off  closely.  Evaporate  the 
ethers  slowly  on  a  steam  bath,  then  dry  the  fat  in  a  boiling  water 
oven  to  constant  weight. 

Confirm  the  purity  of  the  fat  by  dissolving  in  a  little  pe- 
troleum ether.  Should  a  risidue  remain,  remove  the  fat  com- 
pletely with  petroleum  ether,  dry  the  residue,  weigh  and  deduct 
the  weight.  Finally  correct  this  weight  by  a  blank  determina- 
tion on  the  reagents  used." 

SWEETENED  CONDENSED  MILK. 
Preparation  of   Sample. 

Pour  the  contents  of  the  can  into  a'  bowl  or  on  a  glass  plate. 
Scrape  out  the  can  thoroughly,  removing  all  the  sugar  sediment 
from  the  top  and  bottom  of  the  can.  Mix  thoroughly  with  pestle 
or  spatula  until  a  homogenous  emulsion  is  secured.  This  is 
important,  as  it  is  exceedingly  difficult  to  secure  a  representative 
sample  otherwise. 

If  it  is  desired  to  use  a  40  per  cent  solution  as  directed  in 
the  determination  of  the  individual  ingredients,  weigh  accurately 
40  grams  of  the  properly  mixed  contents  of  the  can  into  a  100  c.c. 
graduated  flask.  Add  60  c.c.  of  water.  The  sweetened  con- 
densed milk  mixes  somewhat  difficultly  with  the  water.  Complete 
solution  is  facilitated  by  adding  the  water  in  several  install- 
ments, shaking  after  each  addition  until  condensed  milk  sedi- 
ment adheres  no  longer  to  the  bottom  and  sides  of  the  flask. 

Specific  Gravity. 

Aerometric   Method  by   Means   of   Beaume   Hydrometer. 

Apparatus. 

Beaume  Hydrometer. — L'se  a  specially  constructed  Beaume 
hydrometer  with  mercury  bulb,  and  a  scale  of  30  to  37  degrees  B., 
graduated  to  tenths  degrees.  Length  over  all,  twelve  inches; 
length  of  spindle,  six  inches ;  length  of  empty  bulb,  four  and 


354  CHEMICAL  TESTS  AND  ANALYSES 

one-quarter  inches ;  width  of  empty  bulb,  thirteen-sixteenths  of 
one  inch. 

Hydrometer  Jar. — Use  a  glass  or  tin  cylinder  with  substantial 
base,  minium  length  twelve  inches,  minimum  width  one  and  a 
half  inches. 

Determination. 

Use  the  original  undiluted  condensed  milk.  The  Beaume  hy- 
drometer is  graduated  to  read  correctly  at  60  degrees  F.  (15.5  de- 
grees C.).  At  this  temperature  the  sweetened  condensed  milk  is 
too  viscous  for  rapid  and  accurate  work.  Warm  the  condensed 
milk  to  100  degrees  F.  or  above  and  correct  the  Beaume  reading 
by  adding  to  the  observed  reading  .025  points  for  every  degree 
Fahrenheit  above  60.  At  a  temperature  of  100  degrees  F.  or  above, 
the  reading  can  be  made  in  fifteen  minutes  or  less,  after  the  hydro- 
meter is  inserted  in  the  milk. 

The  specific  gravity  is  determined  by  the  use  of  the  following 
formula : 

c       •<:             <*                144-3 
Specific  gravity  =: 

144.3  _  B 

B  =  Beaume  reading  at  60  degrees  F. 
Example:   Observed  Beaume  reading  at  120  is  31.6. 
Corrected  reading  =31.6+  [(120  —  60)  X  -025]  =33.1. 

144  3 

Specific  gravity  = =  1.2977. 

144.3  _  33.1 

The  following  table  shows  the  specific  gravity  of  sweetened 
condensed  milk  when  the  Beaume  reading  is  known. 


CHEMICAL  TESTS  AND  ANALYSES 


355 


Beaumg 

Specific 
Gravity 

Beaume 

Specific      j 
Gravity 

Beaum6 

Specific 
Gravity 

0 

1.000 

16.5 

1130 

29.7 

1.260 

0.7 

1.005 

17.1 

1.135 

30.2 

1.265 

1.4 

1.010 

1.77 

1.140 

30.6 

1.270 

2.1 

1.015 

18.3 

1.145 

31.1 

1.275 

2.7 

1.020 

18.8 

1.150 

31.5 

1.280 

3.4 

1.025 

19.3 

1.155 

32.0 

1.285 

4.1 

1.030 

19.8 

1.160 

32.4 

1.290 

4.7 

1.035 

20.3 

1.165 

32.8 

1.295 

5.4 

1.040 

20.9 

1.170 

33.3 

1.300 

6.0 

1.045 

21.4 

1.175 

33.7 

1.305 

6.7 

1.050 

22.0 

1.180 

34.2 

1.310 

7.4 

1.055 

22.5 

1.185 

34.6 

1.315 

8.0 

1.060 

23.0 

1,190 

35.0 

1.320 

8.7 

1.065 

23.5 

1.195 

35.4 

1.325 

9.4 

1.070 

24.0 

1.200 

35.8 

1.330 

10.0 

1.075 

24.5 

1.205 

36.2 

1.335 

10.6 

1.080 

25.0 

1.210 

36.6 

1.340 

11.2 

1.085 

25.5 

1.215 

37.0 

1.345 

11.9 

1.090 

26.0 

1.220 

37.4 

1.350 

12.4 

1.095 

26.4 

1.225 

37.8 

1.355 

13.0 

.100 

26.9 

1.230 

38.2 

1.360 

13.6 

.105 

27.4 

1.235 

38.6 

1.365 

14.2 

.110     . 

27.9 

1.240 

39.0 

1.370 

14.9 

.115 

28.4 

1.245 

39.4 

1.375 

15.4 

.120 

28.8 

1.250 

39.8 

1.380 

16.0 

.125 

29.3 

1.255 

40.1 

1.385 

Gravimetric  Determination. 

Dilute  a  measured  portion  of  a  40  per  cent  solution  with  an 
equal  volume  of  water,  use  5  c.c.  of  the  diluted  mixture,  cor- 
responding to  1  gram'  of  the  condensed  milk  and  proceed  as 
directed  under  "Milk." 

Total  Solids. 

Dilute  a  measured  portion  of  a  40  per  cent  solution  with  an 
equal  volume  of  water,  measure  5  c.c.  of  the  diluted  mixture, 
corresponding  to  1  gram  of  the  condensed  milk  into  an  evap- 
orating dish  containing  15  to  20  grams  of  pure  dry  sand  and 
proceed  as  directed  under  "Milk." 

Ash. 

Ignite  the  total  solids  at  very  low-  redness,  cool,  and  weigh. 
See  "Milk." 

Proteids. 
Determine   nitrogen   in   5   c.c.   of   the   40  per  cent  solution 


356  CHEMICAL  TESTS  AND  ANALYSES 

according  to  the  Gunning  method,  see  "Milk,"  and  multiply  the  re- 
sults by  6.38. 

Lactose. 

Dilute  five  grams  of  a  40  per  cent  solution  to  about  40  c.c. 
and  add  .6  c.c.  of  Fehling's  copper  solution.  Nearly  neutralize 
with  sodium  hydroxide,  make  up  to  100  c.c.,  filter  through  dry 
filter  and  determine  lactose  in  an  aliquot  as  directed  under 
"Milk — Determination  of  Lactose." 

Fat. 
Modified  Babcock  Test. 

Weigh  eighteen  grams,  or  measure  16.1  c.c.  of  the  40  per 
cent  solution  into  a  standard  Babcock  milk  test  bottle.  Add 
4  c.c.  of  commercial  sulphuric  acid,  specific  gravity  1.82  to  1.83. 
Shake  immediately  until  acid  is  thoroughly  mixed  with  the  milk. 
Whirl  in  Babcock  tester  for  six  minutes  at  full  speed.  The 
centrifuge  must  run  smoothly.  Stop  the  tester  gradually  and 
remove  the  bottles  carefully  so  as  not  to  break  the  layer  of  float- 
ing curd.  Decant  the  clear  whey  by  slowly  inclining  the  bottle. 
Now  add  two-thirds  of  a  17.6  c.c.  pipette  full  of  water.  After 
thoroughly  shaking  to  emulsify  the  curd  and  to  wash  it  free 
of  sucrose,  add  4  c.c.  sulphuric  acid,  shake,  whirl  and  decant  as 
before.  Then  add  one  17.6  c.c.  pipette  full  of  water,  17.5  c.c. 
of  sulphuric  acid  and  complete  the  Babcock  test  in  the  usual 
way  as  directed  under  "Milk."  Multiply  the  reading  by  2.5. 

This  method  yields  very  satisfactory  results  with  sweetened 
condensed  milk  containing  not  less  than  4  to  5  per  cent  fat. 
With  condensed  milk  of  a  lower  fat  content  the  decanting  of  the 
clear  whey  is  difficult,  since  the  curd  in  the  partly  skimmed 
product  is  too  heavy  to  float  in  the  form  of  a  firm  cheese. 

The  Roese-Gottlieb  Method. 

As   practiced    in   the    Dairy   Laboratory,    Bureau   of   Chemistry, 
Department  of  Agriculture. 

"Weigh  out  4  to  5  grams  of  the  homogeneous  sample  of 
condensed  milk  into  a  Rohrig  tube  (Zeit.  Unters.  Nahr.  u.  Ge- 
nussm.,  1905,  9:531)  or  some  similar  apparatus  and  dilute  with 
water  in  the  tube  to  about  10.5  c.c. — or,  if  preferred,  weigh  into 


CHEMICAL  TESTS  AND  ANALYSES  357 

the  tube  10  to  11  grams  of  a  40  per  cent  solution  of  the  substance 
— add  li  c.c.  of  concentrated  ammonium  hydroxid  (2  c.c.  if  the 
sample  be  sour)  and  mix  thoroughly  with  the  milk.  Add  10  c.c. 
of  95  per  cent  alcohol  and  mix  well.  Then  add  25  c.c.  of  washed 
ethyl  ether  and  shake  vigorously  for  half  a  minute,  then  add  25 
c.c.  of  petroleum  ether  (redistilled  slowly  at  a  temperature  below 
60  degrees  C.  preferably)  and  shake  again  for  half  a  minute. 
Let  stand  20  minutes  or  until  the  upper  liquid  is  practically  clear 
and  its  own  lower  level  constant.  Draw  off  of  the  ether  solution 
as  much  as  possible — usually  0.5  to  0.8  c.c.  will  be  left — into  a 
weighed  flask  through  a  diminutive  quick  acting  filter,  of  selected 
paper.  The  flask  should  always  be  weighed  with  a  similar  one 
as  counterpoise. 

"Re-extract  the  liquid  remaining  in  the  tube,  this  time  with 
only  15  c.c.  of  each  ether,  shaking  vigorously  half  a  minute  with 
each,  and  allow  to  settle. 

"Draw  off  the  clear  solution  through  the  small  filter  into 
the  same  flask  as  before  and  wash  the  tip  of  the  spigot,  the  funnel 
and  the  filter  with  a  few  c.c.  of  a  mixture  of  the  two  ethers  in 
equal  parts  (previously  mixed  and  free  from  deposited  water). 

"For  perfectly  exact  results  the  re-extraction  must  be  .re- 
peated. This  extraction  yields  usually  not  more  than  about  a 
milligram  of  fat,  if  the  previous  ether-fat-solutions  have  been 
drawn  off  closely —  an  amount  averaging  about  .02  per  cent  on 
a  4-gram  charge. 

"Evaporate  the  ether  slowly  on  a  steam  bath,  then  dry  the 
fat  in  a  boiling  water  oven  until  loss  of  weight  ceases. 

"Prove  the  purity  of  the  fat  by  dissolving  in  a  little  pe- 
troleum ether.  Should  a  residue  remain,  wash  the  fat  out  com- 
pletely with  petroleum  ether,  dry  the  residue,  weigh,  and  deduct 
the  weight.  (This  should  not  often  be  necessary.) 

"Finally  deduct  the  weight  obtained  by  blank  determination 
on  the  chemicals  used. 

"By  this  method  practically  absolute  results  can  be  ob- 
tained." 

Sucrose. 

Determine,  by  difference,  deducting  the  milk  solids  (ash 
plus  proteids  plus  lactose  plus  fat)  from  the  total  solids,  or 


358  CHEMICAL  TESTS  AND  ANALYSES 

invert  the  sucrose,  determine,  the  total  invert  sugar,  deduct  frpm 
this  the  lactose  calculated  as  invert  sugar  and  calculate  the 
difference  as  sucrose. 

Milk  Solids. 

Deduct  the  per  cent  sucrose  from  the  per  cent  total  solids. 
The  difference  represents  the  per  cent  milk  solids. 

EVAPORATED  MILK. 
Preparation   of   Sample. 

Shake  the  can  of  evaporated  milk  vigorously  before  opening. 
If,  upon  opening  the  can,  separated  cream  or  small  lumps  of 
butter  are  found  to  adhere  to  the  seams  and  around  the  junction 
of  the  ends  and  the  body,  set  the  can  in  a  water  bath  at  130 
degrees  F.  for  ten  minutes  or  until  all  fat  is  completely  dissolved. 
Then  pour  the  entire  contents  into  a  beaker  and  pour  back  and 
forth  several  times  until  a1  homogeneous  mixture  is  secured.  If 
it  is  known  before  opening  the  can  that  the  contents  are  sep- 
arated, submerge  the  whole  can  in  a  water  bath  at  130  degrees 
F.  for  ten  minutes,  then  shake,  open  and  proceed  as  above. 

If  it  is  desired  to  use  a  40  per  cent  solution,  as  directed 
under  the  determination  of  the  individual  ingredients,  weigh 
accurately  40  grams  of  the  properly  mixed  contents  of  the  can 
into  a  100  c.c.  graduated  flask.  Add  60  c.c.  water  and  mix  thor- 
oughly by  shaking  or  stirring. 

Specific  Gravity. 

Aerometric   Method. 

Apparatus. 

Beaume  hydrometer. — Use  a  special  Beaunie  hydrometer 
with  a  scale  ranging  from  five  to  twelve  points,  graduated  to 
tenths  degrees  and  mercury-weighted.  Length  over  all  eleven 
inches,  length  of  spindle  six  inches,  length  of  empty  bulb  four 
inches  and  width  of  empty  bulb  seven-eighths  inch. 

Hydrometer  jar. — Use  a  glass  or  tin  cylinder  with  substantial 
base.  Minimum  height  ten  inches  and  minimum  width  one  and 
a  half  inches. 

Determination. 

The  Beaume  hydrometer  is  graduated  to  read  correctly  at 
60  degrees  F.  (15.5  degrees  C.).  For  every  degree  Fahrenheit 


CHEMICAL  Tests  AND  ANALYSES  359 

above  60  add  .0313  points  to  the  observed  reading.  For  every 
degree  Fahrenheit  below  60,  deduct  .0313  points  from  the  ob- 
served reading.  9 

The  specific  gravity  is  determined  by  the  use  of  the  following 
formula  : 

145.5 
Specific  gravity  =  =  U5  5  _  R 

B  =  Corrected   Beaume  reading. 

Example:    Beaume  reading  at  80  degrees  F.  is  7.8. 

Corrected   reading   =7.8+  [(80  —  60)  X  .0313]  =8.43. 

Specific  gravity  =   -__:_:=  1.0615. 


Equally  good  results  may  be  obtained  by  diluting  the  evap- 
orated milk  with  an  equal  weight  of  water.  Then  take  the  Que- 
venne  lactometer  reading  at  60  degrees  F.  Multiply  the  reading 
by  2,  add  1000.  and  divide  by  1000. 

Gravimetric  Determination. 

Dilute  the  evaporated  milk  with  four  times  its  weight  of 
water  and  proceed  as  directed  under  "Milk." 

Total  Solids. 
By  Means  of  Specific  Gravity  and  Babccck  Formula. 

Determine  the  specific  gravity  as  above  directed.  Multiply 
by  1000  and  substract  1000.  Then  use  the  following  formula: 


*t 

L  —  The  figure  derived  from  the  specific  gravity  by  above 
calculations. 

f  =  per  cent  fat. 

Example:  Evaporated  milk  tests  7.8  per  cent  fat  and  has  a 
specific  gravity  of  1.0615. 

L  =  (1.0615  X  1000)  —  1000  =  61.5. 

Total  solids  =     6-^-  +  1.2  X  7.8  =;  24.74  per  cent. 

For  rapid  determination  of  the  total  solids  of  evaporated 
milk  the  factory  operator  is  referred  to  the  following  tables  from 
wrhich  the  per  cent  total  solids  may  be  read  at  a  glance  when  the 
Beaume  reading  at  60  degrees  F.  and  the  per  cent  fat  are  known. 


360 


CHEMICAL  TESTS  AND  ANALYSES 


Per  Cent  Solids  of  Evaporated  Milk. 

The    Beaume   Degrees   at  60  Degrees   F.   are   Indicated   in   the 

Horizontal  Line  at  the  Top.   The  Per  Cent  of  Fat  is  Shown 

in  the  Vertical  Column  at  the  Left. 


Beaume  reading  at  60  degrees  Fahrenheit 


FAT 
PER 
CENT 

8.0 

8.1 

8.2 

8.3 

8.4 

8.5 

8.6 

8.7 

8.8 

8.9 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solfds 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 

cent. 

6.0 

21.75 

21.94 

22.13 

22.32 

22.52 

22.71 

22.90 

23.10 

23.29 

23.49 

6.2 

21.99 

22.18 

22.37 

22.56 

22.76 

22.95 

23.14 

23.34 

23.53 

23.73 

6.4 

22.23 

22.42 

22.61 

22.80 

23.00 

23.19 

23.38 

2358 

23.77 

23.97 

6.6 

22.47 

22.66 

22.85 

23.04 

23.24 

23.43 

23.62 

23.82 

24.01 

24.21 

6.8 

22.71 

22.90 

23.09 

23.28 

23.48 

23.67 

23.86 

24.06 

24.25 

2445 

7.0 

22.95 

23.14 

23.33 

23.52 

23.72 

23.91 

24.10 

24.30 

24.49 

24.69 

7.2 

23.19 

23.38 

23.57 

23.76 

23.96 

24.15 

24.34 

24.54 

24.73 

24.93 

7.4 

23.43 

23.62 

23.81 

24.00 

24.20 

24.39 

24.58 

24.78 

24.97 

25.17 

7.6 

23.67 

23.86 

24.05 

24.24 

24.44 

24.63 

24.82 

25.02 

25.21 

25.41 

7.8. 

23.91 

24.10 

24.29 

24.48 

24.68 

24.87 

25.06 

25.26 

25.45 

25.65 

8.0 

24.15 

24.34 

24.53 

2472 

24.92 

2511 

25.30 

25.50 

25.69 

25.89 

8.2 

24.39 

24.58 

24.77 

24.96 

25.16 

25.35 

25.54 

25.74 

25.93 

26.13 

8.4 

24.63 

24.82 

25.01 

25.20 

25.40 

25.59 

25.78 

25.98 

26.17 

26.37 

8.6 

24.87 

25.06 

25.35 

25.44 

25.64 

25.83 

26.02 

26.22 

26.41 

26.61 

8.8 

25.11 

25.30 

25.49 

25.68 

25.88 

26.07 

26.26 

26.46 

26.65 

26.85 

9.0 

25.35 

25.54 

25.73 

25.92 

2612 

26.31 

26.50 

26.70 

26.89 

27.09 

9.2 

25.59 

25.78 

25.97 

26.16 

26.36 

26.55 

26.74 

26.94 

27.13 

27.38 

9.4 

25.83 

26.02 

26.21 

26.40 

26.60 

26.79 

26.98 

.  27.18 

27.37 

27.57 

9.6 

26.07 

26.26 

26.45 

26.64 

26.84 

27.03 

27.22 

27.42 

27.61 

27.81 

9.8 

26.31 

26.50 

26.69 

26.88 

2708 

27.27 

2746 

27.66 

27.85 

28.05 

10.0 

26.55 

26.74 

26.93 

27.12 

27.32 

27.51 

27.70 

27.90 

28.09 

28.29 

,  10.2 

26.79 

26.98 

27.17 

27.36 

27.56 

27.75 

27.94 

28.14 

28.33 

28.53 

10.4 

27.03 

27.22 

27.41 

27.60 

27.80 

27.99 

28.18 

2838 

28.57 

28.77 

10.6 

27.27 

27.46 

2/.6S 

27.84 

28.04 

28.23 

28.42 

28.62 

28.81 

29.01 

10.8 

2751 

2770 

27.89 

28.08 

28.28 

28.47 

28.66 

28.86 

29.05 

29.25 

11.0 

2775 

27.94 

28.13 

28.32 

28.52 

28.71 

28.90 

29.10 

29.29 

29.49 

11.2 

27.99 

28.18 

28.37 

28.56 

28.76 

28.95 

29.14 

29.34 

29.53 

29.73 

11.4 

28.23 

28.42 

28.61 

28.80 

29.00 

29.19 

29.38 

29.58 

29.77 

29.97 

11.6 

28.47 

28.66 

28.85 

29.04 

29.24 

29.43 

29.62 

29.82 

30.01 

30.21 

11.8 

28.71 

28.90 

29.09 

29.28 

29.48 

29.67 

29.86 

30.06 

30.25 

30.45 

CHEMICAL  TESTS  AND  ANALYSES 


361 


Per  Cent  Solids  of  Evaporated  Milk   (Continued). 

The   B/eaume   Degrees   at  60  Degrees   F.   are   Indicated   in   the 

Horizontal  Line  at  the  Top.   The  Per  Cent  of  Fat  is  Shown 

in  the  Vertical  Column  at  the  Left. 


Beaume  reading  at  60  degrees  Fahrenheit 


FAT 
PER 
CENT 

9.0 

9.1 

9.2 

9.3 

9.4 

9.5 

9.6 

9.7 

9.8 

9.9 

Solids 
per 
cent 

Solids 
per 
cent 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent 

6.0 

23.68 

23.88 

24.08 

24.27 

24.47 

24.66 

24.86 

25.06 

25.26 

25.45 

6.2 

23.92 

24.12 

24.32 

24.51 

24.71 

24.90 

25.10 

25.30 

25.50 

25.69 

6.4 

24.16 

24.36 

24.56 

24.75 

24.95 

25.14 

25.34 

25.54 

25.74 

25.93 

6.6 

24.40 

24.60 

24.80 

24.99 

25.19 

25.38 

25.58 

25.78 

25.98 

26.17 

6.8 

24.64 

24.84 

25.04 

25.23 

25.43 

25.62 

25.82 

26.02 

26.22 

26.41 

7.0 

24.88 

25.08 

25.28 

25.47 

25.67 

25.86 

26.06 

26.26 

26.46 

26.65 

7.2 

25.12 

25.32 

25.52 

25.71 

25.91 

26.10 

26.30 

26.50 

26.70 

26.89 

7.4 

25.36 

25.56 

25.76 

25.95 

26.15 

26.34 

26.54 

26.74 

26.94 

27.13 

7.6 

25.60 

25.80 

26.00 

26.19 

26.39 

26.58 

26.78 

26.98 

27.18 

27.37 

7.8 

25.84 

26.04 

26.24 

26.43 

26.63 

26.82 

27.02 

2722 

27.42 

27.61 

8.0 

26.08 

26.28 

26.48 

26.67 

26.87 

27.06 

27.26 

27.46 

27.66 

27.85 

8.2 

26.32 

26.52 

26.72 

26.91 

27.11 

27.30 

27.50 

27.70 

27.90 

28.09 

8.4 

26.56 

26.76 

26.96 

27.15 

27.35 

27.54 

27.74 

27.94 

28.14 

28.33 

8.6 

26.80 

27.00 

27.20 

27.39 

27.59 

27.78 

27.98 

2818 

28.38 

28.57 

8.8 

27.04 

27.24 

27.44 

2763 

27.83 

28.02 

28.22 

2842 

28.62 

28.81 

9.0 

27.28 

27.48 

27.68 

27.87 

28,07 

28.26 

28,46 

28.66 

28.86 

29.05 

9.2 

27.52 

27.72 

27.92 

28.11 

28.31 

28.5,0 

28.70 

28.90 

29.10 

29.29 

9.4 

27.76 

27.96 

28.16 

28.35 

28.55 

28.74 

28.94 

29.14 

29.34 

29.53 

9.6 

28.00 

28.20 

28.40 

28.59 

28.79 

28.98 

29:18 

29.38 

29.5S 

29.77 

9.8 

28.24 

28.44 

28.64 

28.83 

29.03 

29.22 

29.42 

29.62 

29.82 

30.01 

10.0 

28.48 

28.68 

28.88 

29.07 

29.27 

29.46 

29.66 

29.86 

30.06 

30.25 

10.2 

28.72 

28.92 

29,12 

29.31 

29.51 

29.70 

29.90 

30.10 

30.30 

30.49 

10.4 

28.96 

29.16 

29.36 

29.55 

29.75 

29.94 

30.14 

30.34 

30.54 

30.73 

10.6 

29.20 

29.40 

29.60 

29.79 

29.99 

30.18 

30.33 

3058 

30.78 

30.97 

10.8 

29.44 

29.64 

29.84 

30.03 

30.23 

30.42 

30.62 

30.82 

31.02 

31.21 

11.0 

29.68 

29.88 

30.08 

30.27 

30.47 

30.66 

30.86 

31.06 

31.26 

31.45 

11.2 

29.92 

30.12 

30.32 

30.51 

30.71 

30.90 

31.10 

31.30 

31.50 

3L69 

11.4 

30.16 

30.36 

30.56 

30.75 

30.95 

31.14 

3134 

31.54 

31J4 

31.93 

11.6 

30.40 

30.60 

30.80 

30.99 

31.19 

31.38 

3158 

31.78 

31.98 

32.17 

11.8 

30.64 

30.84 

31.04 

31.23 

31.43 

31.62 

31.82 

32.02 

3222 

3241 

362 


CHEMICAL  TESTS  AND  ANALYSES 


Per  Cent  Solids  of  Evaporated  Milk  (Continued). 

The   Beaume   Degrees   at   60   Degrees   F.   are   Indicated   in   the 

Horizontal  Line  at  the  Top.   The  Per  Cent  of  Fat  is  Shown 

in  the  Vertical  Column  at  the  Left. 


Beaume  reading  at  60  degrees  Fahrenheit 


FAT 
PER 
DENT 

10.0 

10.1 

10.2 

10.3 

10.4 

10.5 

10.6 

10.7 

10.8 

10.9 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent  . 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

Solids 
per 
cent. 

6.0 

25.65 

25.85 

26.05 

26.25 

26.45 

26.65 

26.85 

27.05 

27.25 

27.45 

6.2 

25.89 

26.09 

26.29 

26.49 

26.69 

26.89 

27.09 

27.29 

27.49 

27.69 

6.4 

26.13 

26.33 

26.53 

26.73 

26.93 

27.13 

27.33 

27.53 

27.73 

27.93 

6.6 

26.37 

26.57 

26.77 

26.97 

27.17 

27.37 

27.57 

27.77 

27.97 

28.17 

6.8 

26.61 

26.81 

27.01 

27.21 

27.41 

27.61 

27.81 

28.01 

28.21 

28.41 

7.0 

26.85 

27.05 

27.25 

27.45 

27.65 

27.85 

28.05 

28.25 

28.45 

28.65 

7.2 

27.09 

27.29 

27.49 

27.69 

27.89 

28.09 

28.29 

28.49 

28.69 

28.89 

7.4 

27.33 

27.53 

27.73 

27.93 

28.13 

28.33 

28.53 

28.73 

28.93 

29.13 

7.6 

27.57 

27.77 

27.97 

28.17 

28.37 

28.57 

28.77 

28.97 

29.17 

29.37 

7.8 

27.81 

28.01 

28.21 

28.41 

28.61 

28.81 

29.01 

29.21 

29.41 

29.61 

8.0 

28.05 

28.25 

28.45 

28.65 

28.85 

29.05 

29.25 

29.45 

29.65 

29.85 

8.2 

28.29 

28.49 

28.69 

28.89 

29.09 

29.29 

29.49 

29.69 

29.89- 

30.09 

8.4 

28.53 

28.73 

28.93 

29.13 

29.33 

29.53 

29.73 

29.93 

30.13 

30.33 

8.6 

28.77 

28.97 

29.17 

29.37 

29.57 

29.77 

29.97 

30.17 

30.37 

30.57 

8.8 

29.01 

29.21 

29.41 

29.61 

29.81 

30.01 

30.21 

30.41 

30.61 

30.81 

9.0 

29.25 

29.45 

29.65 

29.85 

30.05 

80.25 

30.45 

30.65 

30.85 

31.05 

9.2 

29.49 

29.69 

29.89 

30.09 

30.29 

80,49 

30.69 

30.89 

31.09 

31.29 

9.4 

29.73 

29.93 

30.13 

30.33 

30.53 

80.73 

30.93 

31.13 

31.33 

31.53 

9.6 

29.97 

30.17 

30.37 

30.57 

30.77 

80.97 

31.17 

31.37 

31.57 

31.77 

9.8 

30.21 

30.41 

30.61 

30.81 

31.01 

31.21 

31.41 

31.61 

31.81 

32.01 

10.0 

3(X45 

30.65 

30.85 

31.05 

31.25 

81.45 

31.65 

31.85 

32.05 

32.25 

10.2 

30.69 

30.89 

31.09 

31.29 

31.49 

81.69 

31.89 

32.09 

32.29 

32.49 

10.4 

30.93 

31.13 

31.33 

31.53 

31.73 

81.93 

32.13 

32.33 

32.53 

32.73 

10.6 

31.17 

31.37 

31.57 

31.77 

31.97 

32.17 

32.37 

32.57 

32;77 

32.97 

10.8 

3L41 

31.61 

31.81 

32.01 

32.21 

32.41 

32.61 

32.81 

33.01 

33.21 

11.0 

31.65 

31.85 

32.05 

32.25 

32.45 

32.65 

32.85 

33.05 

33.25 

33.45 

11.2 

31.89 

32.09 

32.29 

32.49 

32.69 

32.89 

33.09 

33.29 

33.49 

33.69 

11.4 

32.13 

32.33 

32.53 

32.73 

32.93 

33.13 

33.33 

33.53 

33.73 

33.93 

11.6 

32.37 

32.57 

32.77 

32.97 

33.17 

33.37 

33.57 

33.77 

33.97 

34.17 

11.8 

32.61 

32.81 

33.01 

33.21 

33.41 

33.61 

33.81 

34.01 

34.21 

34.41 

CHEMICAL  TESTS  AND  ANALYSES  363 

Gravimetric  Determination. 

Dilute  a  measured  portion  of  a  40  per  cent  solution  with  an 
equal  volume  of  water,  use  5  c.c.  of  the  diluted  mixture,  correspond- 
ing to  1  gram  of  the  evaporated  milk  and  proceed  as  directed  under 
"Milk." 

Ash. 

Ignite  the  total  solids  at  very  low  redness,  cool,  weigh,  see 
"Milk." 

Proteids. 

Use  5  c.c.  of  a  40  per  cent  solution,  determine  nitrogen  accord- 
ing to  the  Gunning  method  as  directed  under  "Milk,"  and  multiply 
result  by  6.38. 

Lactose. 

Dilute  10  grams  of  a  40  per  cerit  solution  to  about  40  c.c.  and 
add  .6  c.c.  of  Fehling's  copper  solution;  nearly  neutralize  with 
sodium  hydroxide,  make  up  to  100  c.c.,  filter  through  dry  filter,  and 
determine  lactose  in  an  aliquot  as  directed  under  "Milk." 

Fat. 
The   Modified   Babcock   Method.1 

Carefully  weigh  4.5  grams  of  well-mixed  evaporated  milk  into 
the  8  per  cent  test  bottle.  Add  one  17.6  c.c.  pipetteful  of  water.  Add 
17.5  c.c.  of  sulphuric  acid  and  shake  until  the  curd  in  the  test  bottle 
is  completely  dissolved.  Whirl  at  usual  speed  (one  thousand  revo- 
lutions per  minute)  for  five  minutes.  Mix  equal  portions  of  water 
and  sulphuric  acid  in  glass  beaker.  For  one  or  two  tests,  one 
pipetteful  of  water  and  one  acid  measure  full  of  acid  are  sufficient. 
Fill  test  bottle  to  slightly  below  the  bottom  of  the  neck  with  the  hot 
diluted  acid.  Whirl  for  two  minutes.  If  the  fat  collected  at  the 
base  of  the  neck  is  not  clear,  shake  the  bottle  until  all  the  curdy 
matter  is  completely  dissolved,  fill  the  bottle  to  about  the  8  per  cent 
mark  with  hot  mater,  whirl  for  one  minute  and  read  the  test  at  135 
degrees  F.  The  fat  column  must  be  read  from  the  top  of  the  upper 
meniscus  to  the  bottom  of  the  lower  meniscus.  Multiply  the  reading 
by  4.  This  gives  the  correct  per  cent  of  fat. 

Instead  of  weighing  4.5  grams  into  the  test  bottle,  a  4.3  c.c. 


1  Hunziker  and  Spitzer,  Indiana  Agricultural  Experiment  Station,  Bulletin 
No.  134,  1909. 


364 


CHEMICAL  TESTS  AND  ANALYSES 


pipette  may  be  used.  After  emptying  the  pipette  into  the  bottle  it 
should  be  rinsed  twice  and  the  rinsings  discharged  into  the  test 
bottle. 

For  making  numerous  tests 
from  the  same  sample  it  is  advis- 
able to  dilute  the  evaporated  milk 
with  equal  parts  of  water,  by 
weight;  then  weigh  nine  grams  of 
this  dilution  into  the  test  bottle  and 
add  one-half  pipetteful  of  water. 


S = 


2 =: 


--B 


Read  from  A  to  D 


Pig-.  Ill 
Beading*  the  Babcock  test 


The   Roese-Gottlieb   Method. 

Proceed  as  directed  under 
"Sweetened  Condensed  Milk." 

MILK   POWDER. 

Total  Solids. 

Weigh  5  grams  of  the  milk 
powder  in  a  drying  bottle  or  evap- 
orating dish  and  place  in  drying 
oven  at  100  to  105  degrees  C.  until 
constant  weight  is  secured. 

Ash. 

Weigh  two  grams  of  the  milk  powder  in  a  weighed  platinum 
dish  and  proceed  as  directed  under  "Milk." 

Proteids. 

Use  five  grams  of  the  milk  powder  and  proceed  as  directed 
under  "Milk." 

Milk  Sugar  (Lactose). 

Dissolve  ten  grams  of  milk  powder  in  90  c.c.  of  water.  Warm 
and  stir  until  a  satisfactory  solution  is  effected  and  proceed  as  di- 
rected under  "Milk,"  and  multiply  result  by  10. 

Sucrose. 

For  the  determination  of  sucrose  proceed  as  directed  under 
"Sweetened  Condensed  Milk." 


MOJONNISR  TEST  365 

Fat. 

The  Babcock  Test  Method. — Dissolve  ten  grams  of  milk 
powder  in  90  c.c.  of  water.  Warm  and  mix  until  a  complete  solu- 
tion is  effected.  Then  proceed  as  directed  under  "Milk,"  and  mul- 
tiply the  result  by  10. 

"Roese-Gottlieb  Method. — Weigh  one  gram  of  the  powder 
in  a  30  c.c.  lipped  beaker.  Rub  up  with  9  c.c.  of  water  and  2  c.c.  of 
concentrated  ammonium  hydroxid,  digest  on  steam  bath  until  the 
casein  is  well  softened  and  the  whole  resembles  milk.  Cool,  transfer 
to  Rohrig  tube  or  similar  apparatus,  using  10  c.c.  of  95  per  cent 
alcohol  for  rinsing,  followed,  after  shaking  contents  of  tube,  by  25 
c.c.  of  washed  ethyl  ether.  Shake  vigorously  for  one-half  minute 
and  proceed  as  in  the  determination  of  fat  in  sweetened  condensed 
milk." 

CHAPTER  XXXI. 
THE   MOJONNIER   TEST   FOR   FAT   AND   SOLIDS.1 

The  Mojonnier  test  for  fat  and  solids  in  milk  and  milk  prod- 
ucts represents  the  use  of  chemical  apparatus  and  mechanical  de- 
vices of  a  high  degree  of  precision,  ingeniously  invented,  scientific- 
ally modified  and  especially  adapted  for  accurate  tests  of  dairy  prod- 
ucts. It  offers  methods  of  fat  and  solids  estimations  that  combine 
the  accuracy  of  official  chemical  analysis  with  the  rapidity  of  fac- 
tory tests.  It  has  been  introduced  in  and  is  successfully  used  by 
most  of  the  progressive  milk-condensing  factories  in  the  country, 
and  it  is  admirably  filling  a  long-felt  demand  for  reliable  and  accu- 
rate methods  of  testing  milk,  condensed  milks  and  milk  powders 
and  for  standardizing  these  products  under  factory  conditions. 

EQUIPMENT. 

Install  the  tester  on  a  solid  foundation  in  a  room  protected 
against  excessive  fluctuations  in  temperature. 

1.  Tester  for  butter  fat. 

2.  Tester  for  total  solids. 

3.  Fat  extraction  flasks. 


1  Directions    furnished    through    courtesy    of    Mojonnier   Bros.    Co,,    MUK 
Engineers,  Chicago. 


366 


THE  MOJONNIER  TEST 


4.  Eight  3^-inch  aluminum  dishes  without  covers  and  with 
tall  counterpoise  which  tares  the  eight  dishes,  for  fat  tests. 

5.  Eight  3-inch  aluminum  dishes  with  covers  and  short  coun- 
terpoise, for  solids  tests. 

6.  Fat  oven.     Keep  temperature  at  135°  C. 

7.  Cooling  chamber. 

8.  Solids  oven.     Keep  temperature  at  100°  C. 

9.  250°  C.  thermometer  for  solids  oven.     Have  mercury  bulb 

3031   25  II  7      10    3   136    4 


23     17 


16          29  14        15   19 

Fig-.  112.    The  Mojonnier  tester 
Courtesy  of  Mojonnier  Bros.  Company 


£4 


fit  snugly  into  brass  mercury  well.    Brass  mercury  well  must  always 
form  good  contact  with  hot  plate. 

10.  250°  C.  thermometer  for  fat  oven.    Observe  same  precau- 
tions as  in  (9). 

11.  Vacuum  gauge  on  main  suction  line,  registers  either  or 
both  ovens. 

12.  Solids  plate.     Must  be  level  and  held  at  180°  C. 

13.  Fat  plate.     Hold  at  135°  C. 


THE  MOJONNIER  TEST  367 

14.  Rheostat  for  fat  plate.     Lever  must  make  good  contact 
with  one  button,  not  with  two  at  a  time.  When  right  button  has  been 
found  that  maintains  constant  temperature,  mark  this  point  on  rheo- 
stat rim.     When  starting  tester  each  day,  turn  handle  on  full  until 
temperature  has  risen  to  within  right  point,  then  turn  back  to  previ- 
ously marked  button. 

15.  Rheostat  for  fat  oven.     Observe  same  precautions  as  in 
(14). 

16.  Rheostat  for  solids  oven.     Observe  same  precautions  as 
in  (14). 

17.  Rheostat  for  solids  plate.     Observe  same  precautions  as 
in  (14). 

18.  Handle  for  centrifuge. 

19.  Snap  switches  for  each  hot  plate  showing  temperature  and 
time  for  treating  samples  at  various  points. 

20.  Power  unit,  consisting  of  vacuum  pump,  water  circulating 
pump  and  motor  for  same.     Keep  pump  filled  to  air  cock  with  oil 
furnished  with  tester. 

21.  Automatic  burettes  and  cans  holding  the  water,  ammonia, 
alcohol,  ethyl  ether  and  petroleum  ether,  placed  in  the  order  in  which 
they  are  used.    Each  division  on  burettes  delivers  the  proper  amount 
of  the  desired  reagent  for  a  single  extraction. 

22.  Hood,  to  be  placed  over  fat  dishes  when  evaporating  off 
ether. 

23.  Legs,  to  be  fastened  to  floor  with  lag  screws. 

24.  This  side  need  not  be  fastened  to  floor.     If  necessary  to 
take  out  power  unit  disconnect  connections  in  rear  of  machine  and 
move  this  part  of  machine  forward. 

25.  Chemical  balance.    Keep  level,  clean  and  handle  carefully. 
Raise  knife  edges  gradually  and  with  care.     Clean  balance  daily. 
Keep  weights  clean.    When  weights  show  signs  of  wear,  order  new 
ones. 

26.  Cock,  to  exhaust  vacuum  from  oven  when  cock  (27)  is 
closed.     Must  be  kept  closed  when  vacuum  is  turned  on  oven. 

27.  Cock,  that  switches  vacuum  from  main  line  into  vacuum 
oven.     Set  of  cocks  at  right  is  for  solids  oven,  set  of  cocks  at  left 
is  for  fat  oven. 

28.  Hole  in  top  of  fat  plate  holder,  communicating  with  suction 


368  THE  MOJONNIKR  TEST 

,1 

fan,  on  power  unit.  Run  exhaust  pipe  on  suction  fan  out  of  window 
and  keep  hood  over  the  dishes  in  order  to  drive  all  ether  fumes 
from  room. 

29.     Stool,  to  be  screwed  to  floor. 

DIRECTIONS  FOR  OPERATING  MOJONNIER  TEST. 

Preliminary    directions    for    tests    of    both    Fat    and    Solids. 

(1)  Wash  solids  dishes  with   warm  water  and  fat  dishes 
with  gasoline.     Dry  with  a  towel  and  place  into  heated  vacuum 
oven  for  five  minutes  with  vacuum  on.  At  the  end  of  five  minutes 
put  these  dishes  into  cooler  and,  with  the  pump  still  running, 
keep  them  there  for  five  minutes  before  weighing.     Do  not  turn 
off  motor  until  last  dish  is  weighed  out  of  cooling  chamber. 

(2)  While     dishes     are     being     heated     and     cooled,     wash 
pipettes    with    water,    alcohol    and    ether    and    dry   by    applying 
vacuum   at   exhaust   cock   upon   tester.     Always  use  clean   and 
dry  pipettes  for  each  different  sample.     Aim  to  clean  pipettes  as 
well  as  all  glassware,  immediately  after  using. 

(3)  It  is  very  important  to  keep  extraction  flasks   clean. 
Wash  these  with   warm  water  immediately  after  extraction   is 
finished.    Wash  with  washing  powder  and  shot  when  necessary. 

(4))  After  aluminium  dishes  have  been  in  cooler  for  at 
least  five  minutes,  weigh  accurately  to  .0001  gram,  using  the 
proper  counterpoise.  Weigh  solids  dishes  with  cover  on.  Fat 
dishes  do  not  have  covers.  Fat  dishes  should  be  cooled  for 
seven  minutes  before  being  weighed. 

(5)  Us£  weighing  pipettes  as  follows:   Fill  five-gram  pipette 
up    to    five-gram    mark    for    butter    fat,    and    one-gram    pipette 
up  to  one-gram  mark  for  total  solids.     If  duplicates  are  to  be  run 
fill  two  pipettes  from  the  same  sample.     As  pipettes  are  filled 
place  lower  end  into  cleaned  and  dry  rubber  tubes  which  are 
pressed  upon  knobs  at  ends  and  center  of  weighing  cross.    Either 
five  or  less  samples  for  butter  fat  or  five  or  less  for  total  solids 
may  be  pipetted  out. 

(6)  Weigh  the  cross  with  the  pipettes  containing  the  milk 
on  chemical  balance  accurately  to  .0001   gram.     Run  milk  from 
pipette  into  proper  flask,  or  3-inch  dish  if  making  solids  test. 
The  pipettes  may  be  distinguished  by   the   number  upon   each 


THK  MOJONNIKR  TEST  369 

cross.  Replace  pipette  and  weigh  again.  Difference  in  weight 
gives  weight  of  sample.  Repeat  until  all  samples  are  run  into 
proper  flasks,  and  into  weighed  solids  dishes  if  solids  are  deter- 
mined along  with  the  fat. 

For  fat  in  Sweetened  Condensed  Milk  use  a  five-gram 
sample.  The  five-gram  pipette  delivers  approximately  five 
grams  between  the  five-gram  mark  and  the  base  of  the  bowl  of 
the  pipette. 

Some  operators  prefer  to  mix  200  grams  of  sweetened  con- 
densed milk  with  200  grams  of  water,  weighing  these  carefully 
upon  a  Harvard  trip  scale  sensitive  to  .1  gram.  In  this  case  care 
must  be  exercised  to  obtain  the  exact  weight  of  both  milk  and 
water  and  to  stir  these  thoroughly  with  glass  or  metal  rod  before 
taking  sample.  A  tall  tumbler,  a  one-pound  bottle  or  a  quart 
cup  make  good  containers  in  which  to  make,  mixture.  A  ten- 
g-ram  sample  of  this  mixture  is  used.  This  is  best  weighed  out 
by  using  two  five-gram  pipettes  on  weighing  cross. 

For  total  solids  weigh  out  ^  (.5000)  to  ^4  (.7500)  gram  of 
this  mixture.  If  the  undiluted  milk  is  used  take  as  nearly  (.2500) 
gram  as  possible. 

For  regular  8  per  cent  plain  bulk  condensed  milk  use  same 
size  samples  and  treat  same  as  evaporated  milk.  For  12  per  cent 
superheated  condensed  milk  mix  100  grams  milk  with  300  grams 
water  upon  Harvard  trip  scale.  Weigh  ten-gram  sample  of  this 
mixture  into  flask  for  fat  and  a  two-gram  sample  into  solids 
dish  for  solids.  Multiply  percentages  obtained  by  four  for  cor- 
rect percentages,  when  a  1  to  4  dilution  is  made. 

FRESH  MILK,  SKIM  MILK,  WHEY,  BUTTERMILK. 
Butter  Fat  Determination. 

(1)  Use  the  ten-gram  pipettes  for  measuring  out  ten  grams 
of  milk  into  cleaned  but  not  necessarily  dried  Mojonnier  extrac- 
tion flask.  Use  only  ten-gram  pipettes  furnished  with  tester 
and  do  not  use  10  c.c.  pipettes.  The  pipette  is  graduated  to 
deliver  ten  grams  of  milk  after  allowing  all  milk  to  run  out 
and  letting  it  drain  for  fifteen  seconds  longer,  then  blowing 
gently  to  remove  last  drop.  .The  pipette  must  be  perfectly  clean 
and  dry  before  being  used.  Wash  frequently  with  sulphuric  acid, 
water,  alcohol  and  ether  to  insure  having  a  clean  pipette. 


370  THE  MOJONNIER  TEST 

(2)  Make  extractions  exactly  as  in  test  for  butter  fat  in 
condensed  milk,  excepting  that  in  second  extraction  only  15  c.c. 
of  each  ether  need  be  used. 

(3)  Percentage  butter   fat   is   obtained  by   multipling  the 
weight  of  the  extracted  butter  fat  by  10. 

(4)  If  any  of  these  products  have  soured  badly,  double  the 
quantity  of  ammonia  in  the  regular  extraction  and  shake  until 
all  particles  are  dissolved. 

Total  Solids  Determination. 

(1)  Determine  total  solids  as  in  evaporated  milk,  excepting 
that  a  two-gram  sample  is  weighed  out,  and  no  water  need  be 
added  to  spread  the  milk  over  the  bottom  of  the  dish. 

SWEETENED  CONDENSED  MILK,  EVAPORATED  MILK 
AND  CONDENSED  BULK  MILK. 

Butter  Fat  Determination. 

(1)  Remove  flask  from  holder  and  run  4  c.c.  water   (one 
charge  on  water  burette)  into  each  flask.     Be  careful  not  to  add 
more.    Shake  well  until  all  of  sample  is  mixed  with  water.    This 
can  be  done  without  inserting  cork. 

For  Sweetened  Condensed  Milk,  if  not  diluted  with  water, 
add  6  c.c.  of  hot  water  with  a  pipette.  To  get  hot  water  place  fat 
dish  filled  with*  distilled  water  upon  solids  plate.  If  sweetened 
milk  has  been  previously  diluted  with  water  and  a  ten-gram 
sample  has  been  used,  it  is  not  necessary  to  add  water. 

It  is  very  necessary  to  shake  the  flasks  containing  the  sweet- 
ened condensed  milk  very  thoroughly  after  the  addition  of  each 
reagent.  Sweetened  condensed  milk  requires  more  shaking 
than  any  other  liquid  milk  product. 

(2)  Before  replacing  flask  into  holder,  add  \l/2  c.c.  c.p.  am- 
monia.    Shake  well   so  that  all  of  sample  is  well   mixed   with 
ammonia.     This  can  be  done  without  inserting  cork. 

(3)  Add  95  per  cent  alcohol  up  to  base  of  top  bulb  of  ex- 
traction flask.     Insert  cork,  using  best  quality  corks  only.     Re- 
place flask  into  flask  holder.     Shake  thoroughly  and  see  that  no 
milk  adheres  to  any  part  of  flask  undissolved.     In  case  particles 
of  milk  stick  to  side  of  flask,  shake  thoroughly  until  these  are 


THE;  MOJONNIER  TEST  371 

washed  away.     It  is  of  the  utmost  importance  to  shake  thor- 
oughly at  this  point. 

(4)  Add  25  c.c.  ethyl  ether,  insert  cork  and  shake  vigorous- 
ly, lengthwise  of  flask,  with  liquid  in  large  bulb  of  flask,  and 
small  bulb  extended  upward.    Stop  shaking  at  end  of  five  seconds 
until  all  liquid  has  run  into  large  bulb  and  repeat  vigorous  shak- 
ing for  four  five-second  periods. 

(5)  Add  25  c.c.  petroleum  ether  and  shake  in  same  way. 

(6)  Place  extraction   flasks  into  centrifuge  and  whirl   for 
thirty  turns  at  speed  of  about  600  R.  P.  M.     Double  time  for 
sweetened  condensed  milk. 

(7)  Place  four  3*/2-inch  dishes  in  line  on  shelf  adjoining  hot 
plate,  keeping  them  in  order  in  which  their  weights  were  posted 
upon  record  sheet.     Aim  to  have  numbers  on  flasks  correspond 
with  number  of  dishes. 

(8)  Pour  ether  extraction  to  dividing  line  into  proper  dishes 
and  slide  dishes  over  onto  hot  plate,  which  should  be  held  at  a 
temperature  of  135  degrees  C.,  as  indicated  by  thermometer  in- 
serted in  nickel  plated  mercury  well. 

(9)  Repeat  the  extraction,  adding  first  alcohol  enough  to 
bring  line  close  up  to  top  of  small  neck  of  flask,  then  25  c.c. 
ethyl  ether,  and  then  25  c.c.  petroleum  ether,  and  shake  vigorous- 
ly after  the  addition  of  each  of  above  three  reagents  for  four 
5-second  periods. 

(10)  Whirl  in  centrifuge  for  thirty  turns. 

(11)  Move  aluminum  dishes  back  upon  shelf  adjoining  hot 
plate  and  pour  the  second  extraction  into  proper  dishes.     Never 
pour  extraction  into  hot  dish.     Remove  dish  from  hot  plate  as 
soon  as  ether  is  all  evaporated. 

(12)  When  all  of  ether  has  evaporated  place  dishes  into 
vacuum  oven,  which  should  have  a  temperature  of  135  degrees 
centigrade.     Keep  them  there  for  five  minutes  after  the  vacuum 
gauge  showrs  at  least  twenty-two  inches  of  vacuum. 

(13)  Place  dishes  into  cooler  for  seven  minutes,  with  pump 
outfit  running.    See  that  water  is  running  through  cooling  plates. 

(14)  Place   counterpoise    for   dish    and   the    approximate 
weight  for  fat  on  right  hand  balance  pan. 


372  THE:  MOJONNIER  TKST 

(15)      Transfer   dish   to   left   hand   balance   pan   and    weigh 
quickly  to  0.10  milligram   (0.0001   gr.). 

(16V      Weight  of  fat  divided  by  weight  of  sample  taken, 
multiplied  by  100,  represents  per  cent  butter  fat. 

Total  Solids  Determination. 

(1)  The  temperature  of  the  hot  plate  in  the  solids  vacuum 
oven  must  be  100  degrees  C.     The  temperature  of  the  outside 
solids  plate  must  be  170  degrees  to  180  degrees  C. 

(2)  To  weighed  milk  in  solids  dish  add  about  1  c.c.  water 
and  distribute  mixture  evenly  over  bottom  of  dish.     For  sweet- 
ened condensed  milk  use  hot  water. 

(3)  Place  not  more  than  two  dishes  at  once  upon  hot  plate, 
which   must  be  perfectly   level.     Allow   all   visible  moisture  to 
evaporate.     During  the  evaporation  turn  the  dishes  around  with 
crucible  tongs,  slowly,  so  as  to  produce  an  even  boiling  over  the 
whole  bottom  surface  of  the  dishes.     The  dishes  must  be  watched 
carefully  during  the  evaporation.     This  step  should  require  not 
more  than  two  minutes.     The  end  point  is  reached  when  bubbling 
and    crackling    ceases    and    sample    shows    first    trace    of    brown. 
Vigorous  boiling  without  spattering  and  complete  evaporation 
are  fundamentally  essential. 

(4)  Place  dishes  into  vacuum  oven,  which  must  be  at  100 
degrees  C.,  and  turn  on  the  vacuum.     Heat  for  ten  minutes.    In 
the  case  of  sweetened  condensed  milk  keep  it  for  twenty  minutes 
in    vacuum    oven.      The    gauge    should    register    not    less    than 
twenty-two   inches   of  vacuum.      If  for  any   reason   you   cannot 
obtain  at  least  twenty-two  inches  of  vacuum  then  leave  dishes 
in  oven  for  twice  the  regular  time. 

(5).    Remove  from  oven  and  place  into  cooler.     Allow  dishes 
to  cool  for  five  minutes. 

(6)  Weigh  dishes  with  covers  on  in  the  same  manner,  that 
the    butter    fat    dishes    were    weighed,    being    careful    to    weigh 
quickly  and  very  .exactly. 

(7)  Weight  of  dry  solids  divided  by  weight  of  milk  taken, 
multiplied  by  100  represents  per  cent  total  solids. 


THE  MOJONNIER  TEST  373 

POWDERED  MILK  AND   MALTED  MILK. 

Method  of  Sampling. 

Mix  the  sample  thoroughly,  making  sure  that  it  is  sufficiently 
pulverized  and  representative  of  the  entire  lot  to  be  tested.  Trans- 
fer the  pulverized  sample  promptly  to  a  sealed  jar.  Mix  before 
removing  portions  for  testing. 

Butter  Fat  Determination. 

(1)  Weigh  out  rapidly,  to  prevent  absorption  of  moisture 
from  the  air,  about  one  gram  of  milk  powder  into  butter  boat. 
In  case  of  malted  milk,  weigh  out  a  0.5  gram  sample. 

(2}  Add  8.5  c.c.  of  hot 'water  to  flask.  Insert  cork.  Heat 
flask  in  water  bath  and  shake  thoroughly  until  the  sample  is 
well  mixed. 

(3)  Add  1.5  c.c.  (one  charge)  ammonia,  and  shake  thor- 
oughly. 

(4}  Add  alcohol  up  to  line  on  small  neck  of  flask.  Insert 
cork.  Replace  flask  into  flask  holder.  Shake  flask  thoroughly 
with,  cork  inserted.  Use  best  quality  cork  only. 

(5)  Cool   flask  by  running  cold   water  over  lower  end  of 
extraction    flask,    if    flask    is    very    hot.      This    is    not    ordinarily 
necessary. 

(6)  Add  25  c.c.  ethyl  ether.     Insert  cork,  shake  vigorously 
until  all  butter  is  dissolved  out  of  boat.     Then  add  25  c.c.  pe- 
troleum ether  and  repeat  operation. 

(7)  Centrifuge  flasks,  turning  handle  thirty  turns  after  cen- 
trifuge has  reached  a  speed  of  about  600  R.  P.  M. 

(8)  Pour  off  extractions  into  proper,  weighed  3^-inch  alum- 
inum dishes.    Repeat  above  extraction,  adding  first  alcohol,  then 
25  c.c.  of  each  ether.     Excepting  for  very  accurate  work  a  third 
extraction  is  not  necessary. 

The  second  extraction  will  remove  all  but  .10  to  .15  per  cent 
of  the  butter  fat.  For  factory  control  work  this  would  be  a  good 
margin  of  safety. 

(9)  Evaporate  off  ether  at   135  degrees  C.  on  "fat  plate," 
and  when  all  of  ether  is  off,  dry  fat  in  fat  oven  held  at  135  de- 
grees C.   for  five  minutes  after  the  vacuum  has  reached  at  least 
twenty-two  inches. 

(10)  Cool,  weigh  and  calculate  per  cent  butter  fat. 


374  BACTERIOLOGICAL  ANALYSES 

Total  Solids  Determination. 

(1)  Use  .3000  gram  sample.     Add  2  c.c.  distilled  water  to 
the  sample  in  this  dish.    Mix  milk  powder  and  water  thoroughly 
with  the  blunt  rod. 

(2)  Continue  the  determination  as  under  evaporated  milk, 
but  continue  heating  in  the  vacuum  oven  for  twenty  minutes. 

CHAPTER  XXXII. 
BACTERIOLOGICAL    ANALYSES. 

While  it  is  obviously  beyond  the  scope  and  purpose  of  this 
volume  to  discuss  in  detail  the'  technique  of  bacteriological 
analyses  and  microscopic  preparations  of  the  milk  products  de- 
scribed herein,  it  is  deemed  advisable  to  offer  some  suggestions 
that  may  serve  for  guidance  of  those  who  are  not  familiar  with 
bacterial  fermentations  in  condensed  milk. 

Sampling. — Take  samples  of  all  products  contained  in  open 
receptacles,  such  as  fluid  milk,  plain  condensed  bulk  milk,  barreled 
sweetened  condensed  milk  and  milk  powder,  in  sterile,  cotton 
plugged  test  tubes,  or  in  small  sterile  glass-stoppered  bottles, 
and  keep  them  in  a  cool  place,  preferably  not  above  35  degrees 
F.  until  ready  to  use.  Keep  canned  condensed  milk  sealed  in 
the  original  package  until  ready  to  use.  If  already  open,  invert 
a  petri  dish  or  a  beaker  over  the  can  to  avoid  contamination 
from  the  air. 

Dilution  for  Numerical  Counts. — Make  dilutions  in  250  c.c. 
glass-stoppered  flasks.  Before  opening  sealed  cans,  thoroughly 
wipe  off  the  entire  top  with  a  sterile  piece  of  cheese  cloth  soaked 
in  a  saturated  solution  of  mercuric  bichloride  or  a  5  per  cent 
solution  of  carbolic  acid  and  flame  the  top  of  the  can.  Open 
evaporated  milk  cans  by  punching  a  hole  into  their  top,  large 
enough  to  insert  the  discharge  end  of  a  graduated  pipette.  Open 
sweetened  condensed  milk  cans  with  a  sterile  knife  or  a  sterile 
can  opener. 

Jn  the  case  of  fluid  milk  and  evaporated  milk,  measure  with 
a  sterile  graduated  pipette  two  cubic  centimeters  of  the  product 
and  198  cubic  centimeters  of  sterile  water  into  the  250  c.c.  flask. 
In  the  case  of  plain  condensed  bulk  milk,  sweetened  condensed 


BACTERIOLOGICAL  ANALYSES  375 

rnilk  and  milk  powder,  use  tared  flasks  holding  about  150  cubic 
centimeters,  weigh  into  them  two  grams  of  the  product  and  add 
enough  sterile  water  at  a  temperature  of  98  degrees  F.  to  make 
up  100  cubic  centimeters.  Use  a  sterile  spoon  or  spatula  to 
transfer  the  product  to  this  flask.  A  wide-mouth  flask  is 
preferable. 

The  above  represents  the  first  dilution.  The  flask  should  be 
carefully  shaken  until  a  homogeneous  mixture  is  obtained  and 
the  soluble  portions  have  been  completely  dissolved. 

From  this  dilution  further  dilutions  are  made  in  sterile 
water  in  glass-stoppered  flasks,  according  to  requirements.  The 
dilutions  should  be  sufficient  to  limit  the  number  of  colonies  on 
the  plates  to  about  50  to  100  per  plate.  Whole  milk,  as  it  arrives 
at  the  factory,  usually  shows  from  100,000  to  1,000.000  bacteria 
per  c.c.  Evaporated  milk  should  be  practically  sterile  unless  the 
can  shows  signs  of  fermentation  in  which  case  the  number  of 
bacteria  present  will  depend  on  the  age  of  the  sample  can ; 
dilutions  as  high  as  1 : 1,000,000  are  recommended  in  such  cases. 
Plain  condensed  bulk  milk  when  fresh  contains  from  about 
1,000  to  100,000  bacteria  per  c.c.,  when  several  days  old  and  in 
the  absence  of  refrigeration,  its  germ  content  is  often  much 
greater.  Sweetened  condensed  milk  averages  from  about  500  to 
500,000  bacteria  per  c.c. 

Plating. — -For  plating  the  following  media  are  recommended  : 

Media  for  Total  Counts  and  also  for  acidifiers 
4  grams  beef  extract 
10  grams  peptone 
30  grams  lactose 
4  grams  sodium  chloride 
12  grams  thread  agar 
1000  c.c.  distilled  water. 
Acidity  0.1  per  cent. 

For  acidifiers  add  1  c.c.  of  sterile  litmus  solution  to  each 
plate  before  pouring  the  agar. 

Media  for  Liquefiers 

4  grams  beef  extract 
10  grams  peptone 


376  BACTERIOLOGICAL  ANALYSES 

30  grams  lactose 
4  grams  sodium  chloride 
150  grams  gelatin 
1000  c.c.  distilled  water. 

Acidity  0.1  per  cent. 
Media  for  Yeasts  and  Molds 
4  grams  beef  extract 
10  grams  peptone 
12  grams  agar 
.  1000  grams  whey 

Acidity  0.2  per  cent. 

Add  1  c.c.  of  sterile  one  per  cent  tartaric  acid  solution  to 
each  plate  before  pouring  the  medium  over  the  dilution. 

Incubation. — Incubate  agar,  litmus  agar  and  whey  agar 
plates  at  35  degrees  C.  (95  degrees  F.)  for  at  least  three  days 
before  making  counts.  Incubate  gelatin  plates  at  21  degrees  C. 
(70  degrees  F.)  for  four  to  five  days  before  making  counts. 

Making  Counts. — The  colonies  on  the  plates  are  counted 
most  conveniently  by  placing  the  plates  over  a  standard  counting 
plate.  In  the  absence  of  such  a  plate,  place  the  petri  dish  upside 
down  on  a  dark  surface  and  draw,  with  a  blue  crayon,  radial  lines, 
dividing  the  field  into  segments.  For  plates  containing  not  to 
exceed  100  colonies  eight  to  sixteen  segments  are  sufficient  for 
easy  counting. 

Qualitative  Determinations. — Numerical  counts  on  the  four 
kinds  of  media  recommended  above  usually  furnish  a  fair  general 
idea  of  the  types  of  bacteria  present. 

For  the  detection  of  gas-producing  species,  nutrient  bouillon 
containing  three  per  cent  lactose  and  three  per  cent  sucrose,  re- 
spectively, in  fermentation  tubes,  or  nutrient  agar  containing 
three  per  cent  lactose  and  three  per  cent  sucrose,  respectively, 
in  test  tubes,  are  serviceable. 

Cans  of  sweetened  condensed  milk  that  show  gaseous  fermen- 
tation (swell  heads)  are  usually  due  to  certain  species  of  yeast, 
which  thrive  best  in  media  containing  sucrose. 

Cans  of  evaporated  miilk  that  show  gaseous  fermentation 
(swell  heads)*  are  usually  caused  by  anaerobic  putrefactive  bac- 


BACTERIOLOGICAL  ANALYSES  377 

teria,  of  which  Plectridium  foetidum  is  a  most  frequent  repre- 
sentative, see  "Blown  Evaporated  Milk,"  Chapter  XXIII.  This  type 
of  micro-organisms  requires  strictly  anaerobic  cultural  conditions. 
Under  limited  laboratory  facilities  the  anaerobic  conditions  are 
best  produced  by  the  use  of  oxygen-absorbing"  chemicals,  such  as 
pyrogallol  to  which  potassium  hydroxide  is  added.  Use  dry 
commercial  pyrogallol  and  potassium  hydroxide  sticks,  in  pro- 
portion .of  1  gram  pyrogallol  to  .7  gram  potassium  hydroxide, 
dissolved  in  about  2  c.c.  of  water. 

Place  50  grams  of  pyrogallol  into  the  bottom  part  of  a  large 
size  desiccator.  Have  the  rim  of  the  desiccator  and  the  cor- 
responding rim  of  the  cover  covered  with  a  mixture  of  half 
paraffine  and  half  bee's  wax.  Pour  into  the  pyrogallol  in  the 
desiccator  100  c.c.  of  water  and  then  throw  in  35  grams  of 
potassium  hydroxide.  Quickly  insert  culture  tubes,  or  plates, 
and  close  the  desiccator  with  the  cover,  turning  the  cover  so  as 
to  secure  a  perfect  seal.  Apply  three  permanent  screw  clamps. 

Anaerobic  germs  of  the  type  of  Plectridium  foetidum  grow 
best  in  freshly  sterilized  milk.  In  the  case  of  Plectridium  foeti- 
dum the  milk  first  curdles,  then  digests,  forming  a  clear  yellow 
liquid.  The  digestion  begins  at  the  surface  and  proceeds  down- 
ward. These  cultures  develop  a  most  penetrating  foul  odor, 
resembling  that  of  spoiled  eggs.1 

The  technique  and  methods  for  :  determining  the  bacteri- 
ological flora  with  reference  to  cultural  and  morphological 
characteristics  of  individual  species  of  microbes  present,  are 
identical  to  those  used  in  the  bacteriological  study  of  milk  and 
other  similar  products,  and  which  are  fully  described  in  standard 
manuals  on  bacteriology. 


1  For  further  details  on  the  technique  of  Anaerobic  Cultures  see  Hunziker 
Review  of  Existing-  Methods  for  Cultivating  Anaerobic  Bacteria.  Journal  of 
Applied  Microscopy  and  Laboratory  Methods,  Vol.  V,  Nos.  3,  4,  5,  6. 


378 


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380 


CONDENSED  MILK  AND  MILK  POWDER 


INDEX 


Accidents,  prevention  of 95 

Acknowledgments    14 

Acid  tests  50 

Addition   of   sugar 63 

Adulterations    271 

Advertisements  384-424 

Agitation  of  sweetened  )      1Q6    w?    m 
condensed  milk  j 

Air  discharge 312 

Air  intake  312 

Albumin     346 

Altitude   88,  89,  90 

Anaerobic    cultures    377 

Anglo-Swiss  Condensed  Milk  Co 21 

Annual   production  of — 

buttermilk  powder   331 

condensed  buttermilk    184 

condensed    milk    26,  29 

cream  powder   278 

malted  milk    335 

milk    powder    278 

Antineuritic    vitamines    215 

Antiscorbutic  vitamines    216 

Antixerophthalmic   vitamines    215 

Arrangement    of    machinery 41,  42 

Ash 203,  208,  344,  355,  363,  364 

Aspergillus  repens    238 

Atmospheric  pressure  88,  89 

B 

Bacillus   panis    i  .265 

Bacterioligical    analyses    374 

Bacteriological  media    375 

Babcock  test   351,  365 

Barometric  condenser   77 

Barrels    110 

Beet  sugar   63,  64 

Beaume   hydrometer    

99.  100,  101,  122,  353,  358 

Beriberi    215 

Bicarbonate  of  soda 147,  156,  157 

Bitter  evaporated  milk 263 

Blow-down  valve    76 

Boiling  point  at  different  vacua... 86,  87 

Boiling   test    51 

Bolting 315 

Borden,   Gail 18 

Borden's  Condensed   Milk  Co 21 

Borden    patent 18 

Brands  of  condensed  milk 196 

Brown  evaporated  milk 269 

Brown  sweetened  condensed  milk... 251 


Buflovak  process  288 

Buflovak    rapid    circulation    evapora- 
tor     168 

Building     and     equipment     for     con- 

denseries    33 

Bulk  milk    162 

Butterfat    

201,  206,  351,  356,  363,  365,  369,  370,  373 

Butterfat  test  54 

Buttermilk,  composition   177 

Buttermilk    powder    330 

annual  output  331 

composition     331 

manufacture    332 

Buttons      in      sweetened      condensed 

milk 237,  241 

Buying    milk    43 

By- Products    Recovery   Co 25 

c 

Calcium  in  milk 253 

Campbell  process   166,  279 

Cane  v sugar    63,  203 

Cans     110,  111 

Can  testers   135 

Can   washing 56 

Care  of  milk  in  factory 57 

Casein  346 

Casing   machines    189 

Catch-all    82 

Chemical   analyses 342 

of  evaporated    milk    358,  370 

of  malted  milk    373 

of  milk    342,  369 

of  milk  powder   364,  373 

of  sweetened  condensed  milk. 353,  370 

Citrates   in   milk 253 

Coils  in  pan 72,  73,  74 

Composition   of — 

buttermilk    177 

buttermilk  powder   331 

condensed   buttermilk    184 

evaporated  milk    205 

milk  powders   315 

plain  condensed  milk 208 

sweetened    condensed    milk 200 

Concentrated  milk   166 

Concentration,   ratio  of 96,    165,  182 

Condensed  buttermilk   176 

Condensed  milk — 

annual  production  in  U.  S 26,  28 

in   different  countries. 29 

cost  of  manufacture 217 

defects    222 


CONDENSED  MILK  AND  MILK  POWDER 


381 


digestibility    212 

factories  in  U.  S 28 

history  and   development 17 

purity    211 

standards  210 

vitamine  properties   215 

Condensers    76-82 

Condensery  floors  33 

Condensing....  68,  119,  163,  173,  179-184 
Continuous    concentrators. .  .25,    167,  171 

Cooling 103,  129,  165,  174 

Cooling    in    sterilizer 143 

Correction  of  Beaume 100,  122 

Cost  of  manufacture .219,  329 

Cream  Production  Co 25 

Curdy    evaporated    milk 253,  259 


Defective   plain   condensed   milk 252 

lumpy    252 

gritty 270 

Defective   evaporated   milk 252 

bitter   263 

brown   269 

curdy    253 

fermented    258 

grainy   257 

metallic    271 

separated    258 

Defective  sweetened  condensed  milk. 222 

blown    242 

brown    251 

buttons    in    237 

cheesy     231 

fermented  242 

lumpy 233 

metallic    251 

putrid    250 

rancid     249 

sandy    223 

settled 228 

thick    231 

Desiccating  chamber  309 

Distribution  of  heat  in  sterilizer 138 

Dome  ". 75 

Dough-drying  processes   '.  .278 

Drainage    in    condenseries 35 

Dried    buttermilk    330 

E 

Ekenberg  process 286 

Equipment  for  condenseries 39-41 

Evaporated    milk 117 

analyses    358 

behavior  toward  heat 158 

composition  205 

condensing     119 

control    .  . .  146 


cooling    129 

cost  of  manufacture 221 

filling : 132 

heating llg 

homogenizing   124 

incubation    162 

sealing 134 

shaking 159 

standards 210 

standardizing    123,  339 

sterilizing     136 

viscosity   tests    '. 145 

Expansion    tank    82 

Exports 198,  199 


Factory   sanitation    54 

Fat-soluble   vitamines    215 

Fat  standard  for  export 211 

Federal    standards 210,    335,  378 

Fermentation  tests   53 

Fermented   evaporated  milk 262 

Fermented       sweetened       condensed 

milk 242 

Filling    evaporated    milk " 132 

Filling    machines 110 

Film-drying   processes    280 

Floor  plans   35-39 

Flux    115 

fractional    sterilization     144 

G 

Gaseous  fermentations 242,  266-268 

Gas  generators   115 

Gas  supply    115 

Gathmann  process    283 

Gaulin  homogenizer   126,  127 

Gebee    seal    Ill 

Glass-lined  tanks   47,  57,  58,  131 

Glucose     273 

Govers   process    287 

Grainy    evaporated    milk 257 

Gray  processes  297,  299,  302 

Grimwade  process    277 

Gritty  plain  condensed  milk 270 

Gunning    method    344 

H 

Hatmaker   process    282 

Heating   milk 59-62,  118 

Heating   the    air 308 

Hebe  product    216,  272 

Helvetia  Milk  Condensing  Co 22 

High  pressure  pumps 107 

Holding   tanks    130,  131 

Homogenizers     127 

Homogenizing     124,  129 

Hotwells    .  .  61 


382 


CONDENSED  MILK  AND  MILK  POWDER 


Imitation    evaporated    milk 216 

annual   output    273 

Imports     ....198,  199 

Incubation    162,  376 

Index  to  advertisers 384 

Inder  to  contents 380-383 

Insects  in  milk  powder 328 

Inspection  of  cans 187 

Insulation   of   piping 42 


Miscibility    320 

Modified    Babcock   test 356,  363 

Mojonnier  evaporated  milk  control..  145 
Mojonnier  test  for  fat  and  solids 365 

N 

Nailing  machines    189 

Nestle-Cham  Condensed  Milk  Co...  21 
New  York  Condensed  Milk  Co... 20,  21 
i\  itrogen  determination  343 


Jacket    in   pan 71 

John  Wildi  Evaporated  Milk  Co 24 

Just  process   281 


Keeping  quality  of — 

malted   milk    334 

milk  powder  325-328 


Labeling  , 187 

Labeling  machines  187 

Lactose 202,  208,  347,  356,  363,  364 

Legal  standards  of  dairy  products  by 

states  378,  379 

Loading  the  sterilizer 138 

Locations  for  condenseries 29 

Lumpy  milk  powder 328 

Lumpy  sweetened  condensed  milk... 

233-236 

M 

McDonald   seal    Ill 

McLachlan  process   292,  294 

Making   bacterial   counts 376 

Malted    milk    332-335 

Marking  cases 190 

Market  prices 196 

Markets   184,  194,  195,  329,  334 

Mercury  column    75 

Merrell-Merrell-Gere    process    294 

Metallic  evaporated  milk 270 

Metallic  sweetened  condensed  milk.. 251 

Meyenberg,  John  B 23 

Milk   analyses    342 

Milk  inspection   49 

Milk   powder 276-335 

Milk  powder   factories 278 

Milk  prices   45 

Milk  quality 47,  48 

Milk  solids   201,  205,  358 

Milk  sugar  202,  208,  347,  363,  364 

Milk   supply    30,  43 

Milk  trap    82 

Mineral    matter    203,  208 


Operation  of  pan 94 


Packing 183,    189,  315 

for  export  191 

Passburg  process    284 

Percy   process    291 

Phosphates  in  milk 253 

Pilot   sterilizer    142,  143 

Plain  condensed  bulk  milk.  162-165,  208 

Plating   375 

Plectridium  fcetidum  267 

Polyneuritis    215 

Precondensing   for  drying 303-307 

Preface    7,  8 

Preheating    163,    173,  303 

Progress    homogenizer    127 

Proteids   ....  145,  202,  207,  354,  363,  364 
Putrid  sweetened  condensed  milk. . .  .250 


Quality  of  milk 117,  163,  253 

Quevenne  lactometer  342 


Rancid    sweetened   condensed    milk.  .249 

Rapidity    of    evaporation 91 

Ratio  of  concentration 96,  165,  182 

Retardation     152 

Recovery 307,  313 

Rim    speed 173 

Rogers   process    296 

Roese-Gottlieb  method. 352,  356,  364,  365 

Ruff  condensing  evaporator 174 

Rust  spots  on  labels 188 

s 

Sampling  sweetened  condensed  milk.  102 
Sandy   sweetened   condensed   milk... 

223-228 

Sanitary  can   110,  111,  112 

Science  and  practice  of   evaporation 

in  vacuo  85 

Scurvy    216 

Sealing    112,  134 

Sediment    test    .52 


CONDENSED  MILK  AND  MILK  POWDER 


383 


Separated  evaporated   milk ;258-261 

Settled   sweetened   condensed  milk.. 

107,  228-230 

Sewage  disposal 32 

Shaking 159 

Shakers    160 

Size  of  cans  in  sterilizer 142,  156 

Solder     114 

Soldering  devices   113 

Soldering  flux   115 

Solder  seal   Ill 

Solubility  of  milk  powders 318 

Sour,  curdled  evaporated  milk 262 

Specific    gravity    

101,  123,  204,  208,  342,  353,  358 

Spray-drying  processes  290-315 

Spraying  milk    309 

Spray    nozzles    310 

Spray  pumps    31 1 

Spy  glasses  75 

Stamping   of    cans loo 

Standardizing — ^ 

evaporated  milk  123,  336 

fluid  milk . 339 

sweetened  condensed  milk.  118,  340,  341 
Standardization     of     sterilizing     pro- 
cess  143 

Starting    the    pan 94 

Stauf   process    291 

Sterilizers 137 

Sterilizing  process    136 

Sterilizing  sample  cans 149 

Stopping  reel  in  sterilizer 141 

Storage  183-193 

Striking   96,  120,  164 

Sucrose    203,   357,  364 

Sugar    63-67,  203 

Superheating.  120,  141,  163,  225,  232,  261 

Surface  condenser    76 

Sweetened  condensed  milk — 

analyses    353 

composition     200 

cooling    103 

cost  of  manufacture 220 

defects    222 

drawing   off    103 

filling    110 

manufacture 59 

sampling     102 

standard :210 

striking     96 


Table  of  contents 9-14 

Tell-tale  thermometers   139 

Temperature  of  storage 193 

Temperature   in    sterilizer 140 

Testing    for    density 178 

Testing    for   viscosity 150 

Thermometer  for  vacuum  pan 76 

Thick    and    cheesy    sweetened    con- 
densed milk 231-233 

Tin    shop    equipment 41 

Total   solids    

343,  355,  359,  364,  370,  372,  374 

Total  solids  tables 360-362 

Transportation    194 

Transportation  facilities  31 


Vacuo,  science  and  practice  of  evapo- 
ration  in    85 

Vacuum  breaker   76 

Vacuum   gauge    75 

Vacuum  pan  68 

Vacuum  pump   83-85 

Vapor   belt    72 

Venthole    cans 133 

Venthole    fillers    ! .....133 

Ventilation    in    condenseries 34 

Viscolizer    128 

Viscosimeter     151 

Viscosity  correction 152 

Viscosity,   factors  influencing 153-155 

Viscosity    tests     150 

Vitamine  properties   215-216 

w 

Water    201,  205 

Water-soluble  vitamines  215 

Water  supply  30 

Wet-vacuum   spray   condenser 78 

Wimmer  process  279 

Wrinkles  on  labels 188 


Xerophthalmia     215 


Yeast    242,  376 


384  CONDENSED  MILK  AND  MILK  POWDER 


INDEX  TO  ADVERTISERS 

Page 

American  Can  Co.,  New  York 385 

Alois  Aufrichtig  Copper  and  Sheet  Iron  Mfg.  Co.,  St.  Louis,  Mo.  386 

Bausch  and  Lomb  Optical  Co.,  Rochester,  N.  Y 386 

Buffalo  Foundry  and  Machine  Co.,  Buffalo,  N.  Y 387 

Burt  Machine  Co.,  Baltimore,  Md 388 

By-Products  Recovery  Co.,  Toledo,  0 389 

J.  G.  Cherry  Co.,  Cedar  Rapids,  la 390 

Colonial  Salt  Co.,  Akron,  0 411 

Creamery  Package  Mfg.  Co.,  Chicago 391 

Cream  Production  Co.,  Port  Huron,  Mich 392 

Davis-Watkins  Dairymen's  Mfg.  Co.,  Chicago 394,  395,  397 

F.  G.  Dickerson  Co.,  Chicago 393 

Dry  Milk  Engineering  Co.,  Chicago 398 

Engineering  Co.,  Fort  Wayne,  Ind 399 

J.  B.  Ford  Co.,  Wyandotte,  Mich 400 

General  Laboratories,  Madison,  Wise 401 

Groen  Mfg.  Co.,  Chicago 402 

Arthur  Harris  &  Co.,  Chicago. 404,  405 

Jensen  Creamery  Machinery  Co.,  Long  Island  City,  N.  Y 403 

John  W.  Ladd  Co.,  Detroit,  Mich 423 

Lathrop  Paulson  Co.,  Chicago 406 

Milk  Drying  Machinery  Co.,  Chicago 407 

Mojonnier  Bros.  Co.,  Chicago 408 

Louis  F.  Nafis,  Chicago 409 

Pfaudler  Co.,  Rochester,  N.  Y 410 

C.  E.  Rogers,  Detroit,  Mich 412,  413 

Rice  and  Adams  Corporation,  Buffalo,  N.  Y 411 

E.  H.  Sargent  &  Co.,  Chicago 414 

Schaefer  Manufacturing  Co.,  Berlin,  Wise 414 

Sharpies  Separator  Co.,  West  Chester,  Pa 415 

L.  Sonneborn  Sons*  New  York 416 

Spray  Drying  Corporation,  New  York 417 

Sturges  and  Burn  Mfg.  Co.,  Chicago ; 420 

C.  J.  Tagliabue  Mfg.  Co.,  Brooklyn,  N.  Y 418 

Taylor  Instrument  Companies,  Rochester,  N.  Y 419 

Torsion  Balance  Co.,  New  York 420 

Union  Steam  Pump  Co.,  Battle  Creek,  Mich 421,  422,  423 


CONDENSED  MILK  AND  MILK  POWDER  385 


CONTAINERS 

for 

Condensed  Milk 

Evaporated  Milk 

Powdered  Milk 


AMERICAN  CAN  COMPANY 

120  Broadway,  New  York,  N.  Y. 

CHICAGO,  ILL.  PORTLAND  SAN  FRANCISCO,  CAL. 

Monroe  Bldg.  ORE.  Mitts  Bldg. 


386 


CONDENSED  MILK  AND  MILK  POWDER 


Efficiency  and  Economy 

ARE   COMBINED  IN  THE  NATIONALLY    KNOWN 
"AUFRICHTIG"    VACUUM    PAN 

Our  Standard  "6'  6""  Pan  will  condense  10,000  pounds 
of  milk  in  one  hour  with  two  coil  and  12,000  pounds 
with  three  coil  system. 

Investigate  the  economically  operated  Jacketed  Hot 
Wells. 

We  manufacture  complete  equipment  used  in  Milk 
Gondenseries  and  Dairies. 

Highest  grades  of  materials  and  best  of  workmanship 
is  put  into  our  equipment. 

Write  for  specifications  and  prices. 

Alois  Aufrichtig  Copper  &  Sheet  Iron  Mfg.  Co. 

Third  and  Lombard  Streets          Saint  Louis,  Missouri 


Model  FFS8 


JauscH  [omb 

Microscopes 

Standards  of  Optical  and 
Mechanical  Efficiency 

lVf^*1Al  17T7QQ  is  especially  suit- 
IVlOael  F  TOO  abie  for  bacterio- 
logical work.  Has  coarse  and  fine 
focusing  adjustments,  with  adjust- 
ment heads  on  side  of  arm;  two  iris 
diaphragms,  three  objectives — includ- 
ing oil  immersion — in  revolving  nose- 
piece;  two  eyepieces  and  an  Abbe  con- 
denser in  quick-acting  screw  sub- 
stage.  Number  of  magnifications  ob- 
tainable ranges  from  50  to  1260.  Con- 
struction is  rugged,  and  black  crystal 
finish  on  arm  and  base  unusually 
durable. 

Write  for  catalog  describing  this 
and  other  models. 

Bausch  &  Ipmb  Optical  (5. 

NEW  YORK       WASHINGTON     SAN  FRANCISCO 

CHICAGO  ROCH  ESTER.  N.Y.  LONDON 

Leading  American  Makers 
of  High  Grade  Optical  Products. 


CONDENSED  MILK  AND  MILK  POWDER  387 


Dry  Milk  Products 

Manufactured  in 

"Buflovak  "  Apparatus 

The  "Buflovak"  Vacuum  Drum  Dryer  is  the 
ideal  apparatus  for  converting  milk  into  pow- 
der form.  The  milk  is  dried  without  the  slight- 
est danger  of  overheating  or  contamination. 
Every  part  of  the  interior  is  accessible,  and  can 
be  easily  cleaned — a  distinctive  feature  of  the 
"Buflovak"  Dryer. 

When  considered  in  the  light  of  steam  con- 
sumption, drying  speed,  output,  quality  and 
drying  cost,  it  is  the  most  economical  milk 
dryer  on  the  market.  Dries  skim  milk,  butter- 
milk, malted  milk  and  other  liquids  containing 
solids. 

The  "Buflovak"  Rapid  Circulation  Evaporator 
is  especially  adapted  for  evaporating  milk  and 
other  delicate  liquids. 

Vacuum  Shelf  Dryers  for  drying  casein  and 
other  products  in  pans  or  trays. 

Catalog  showing  all  types  of  "Buflovak"  Dryers 
and  Evaporators  will  be  mailed  on  request. 


Buffalo  Foundry  &  Machine  C£L 

20  Winchester  Avenue 
BUFFALO,  N.  Y. 

NEW  YORK  OFFICE:  17  BATTERY  PLACE 


388 


CONDENSED  MILK  ,AND  MILK  POWDER 


THIS  MACHINE 

Plays  an  Important  Part  in 
Milk  Canning 

It  labels  as  many  cans^a  day  as  you  require. 

Orders   are  filled    promptly   and 
Storage  facilities  never  overtaxed. 


THE  BURT  LABELING  MACHINE 

Is  used  in  the  small  as  well  as  the  largest  plants  because 
there  is  no  other  way  to  label  cans  so  fast,  neat  and  cheap. 

It  applies  the  label  with  a  hot  moisture-proof  cement 
which  sets  instantly,  thus  preventing  the  label  from  slipping 
while  being  wrapped  around  the  can  and  ensuring  it  always 
being  applied  tight  and  matched  evenly  at  lap.  No  paste  is 
put  on  the  can,  so  there's  no  possibility  of  the  label  discolor- 
ing— it  always  looks  as  though  just  from  the  printer — that 
increases  the  sales  value  of  goods. 

Let  us  tell  you  more  about  the  Burt  Labeler — what  it  does 
and  why  you  should  not  be  without  it.  Just  state  size  of  cans 
used. 

BURT  MA  CHINE  COMPANY 

Labeling,  Wrapping  and  Casing  Machines 

BALTIMORE,  MD. 


CONDENSED  MILK  AND  MILK  POWDER  389 

T'he    By -Products    Recovery    Company 

109  Chamber  of  Commerce  Building       Toledo,    Ohio 

Milk  Products  Department 

Automatic  Concentrators  for  "Evaporated"  Milk, 

"Preserved"  Milk,  Dry  Milk  and 

Sugar  of  Milk  Factories 

Whole  Milk,  Skim   Milk,  Buttermilk  and  Whey  Rapidly  and 

Economically   Reduced   to   High   Concentrates  Without 

the   Aid   of  \7acuum   Pumps,   Condensers,   Water 

or  Expert  Labor 


It  is  More  Economical  It  is  Less  Complicated 

It  is  More  Simple  to  Operate 

No  Water  Requirements  Excepting  for  Cooling 

More  than  100  Machines  Now  in  Use 

Eor  Particulars  Write 

The  By-Products  Recovery  Co.,  Toledo,  0. 


390 


CONDENSED  MILK  AND  MILK  POWDER 


THE 
Cherry  Condensed  Milk  Cooler 


Three  Special  Features 

1.  It  is  equipped  with  the  justly  famous  Cherry  Twin 
Coil. 

2.  The  coils  are  of  special  diameter  to  assure  their  being 
entirely  submerged  at  all  times,  thus  preventing  the  incor- 
poration of  air  into  the  product. 

3.  It  is  equipped  with  a  two-speed  drive.    This  drive  is  a 
clutch  pulley  through  steel  cut  gears.     This  equipment  pro- 
vides for  operating  the  coil  on  high  speed  for  evaporated  or 
plain  condensed  and  on  low  speed  for  sweetened  condensed 
milk.    This  feature  is  exclusive  on  this  type  of  cooling  vat. 


A  Dependable  Outfit 


Where  condensed  milk  is  concerned  the  requirements  call 
for  a  cooling  system  enabling  the  operator  to  maintain  the 
desired  variation  in  temperature  between  the  product  and  the 
cooling  medium  and  to  save  every  minute  of  time  it  is  pos- 
sible to  save  in  handling  the  product.  The  Cherry  Condensed 
Milk  Copier  is  designed  to  accomplish  this  purpose  and  has 
proven  its  efficiency  in  some  of  the  largest  plants  in  the 
country. 

BUTTER  MAKING  EQUIPMENT 

For  the  Condensery  needing  a  complete  Butter  Making 
Outfit  there  is  the  Cherry  Line  of  Creamery  Equipment  to 
cover  every  requirement. 

If  you  are  considering  the  manufacture  of  butter,  let  us 
quote  you  prices  on  your  needs.  Ask  for  our  special  catalog. 

J.  G.  CHERRY  COMPANY 

CEDAR  RAPIDS,  IOWA 

St.  Paul,  Minn.  Tama,  Iowa  Peoria,  111. 


CONDENSED  MILK  AND  MILK  POWDER  391 

The  WIZARD 

Condensed  Milk  Cooler 


DESIGNED  particularly  for  the  condensed 
milk  trade.  It  is  made  extra  deep.  Coil 
is  entirely  submerged,  thus  preventing  the  incor- 
poration of  air  with  the  product  made. 

Coil  has  two  speeds,  composed  of  shifting  cut 
gears  so  that  coil  can  be  run  on  high  speed  for 
evaporated  or  plain  condensed  and  on  low  speed 
for  sugared  condensed. 

Built  either  with  legs  high  enough  to  permit  a  10  gallon 
can  beneath  gate  valve  or  on  standard  height  legs  as  desired. 

It  has  the  patented  Wizard  Multiple  Feed  Coil  either 
2"  or  2l/2"  diameter  as  desired;  large  built-in  brine  box;  and 
the  latter  can  be  fitted  with  direct  expansion  coils  when  de- 
sired. Made  in  sizes  from  300  to  1000  gallons,  equipped 
for  motor  or  belt  drive. 

The  Creamery  Package  Mfg.  Company 

61-7  W.  Kinzie  St.,  Chicago 

Sales  Branches  Everywhere 


392  CONDENSED  MILK  AND  MILK  POWDER 


Ruff  Milk  Condensing  Evaporator 


1920   MODEL   NO.    7 

The  Ruff  Milk  Condensing  Evaporator  condenses  milk  at 
145  degrees  temperature  without  use  of  vacuum,  leaving  the 
albumin  milk  solids  soluble. 

Will  make  a  superior  quality  condensed  milk  of  all  grades 
sold  on  the  market,  such  as  plain  condensed  and  superheated, 
sugared  condensed  milk,  sugared  milk  condensed  for  the 
chocolate  trade,  unsweetened  evaporated,  precondensing  for 
milk  powder,  also  buttermilk. 

A  world  beater  in  connection  with  your  pan  to  pre-heat 
milk  to  210  degrees  for  making  sugared  and  unsweetened 
evaporated,  a  saving  of  15  per  cent  to  18  per  cent  moisture, 
which  is  generally  added  when  milk  is  heated  with  live  steam. 

This  evaporator  is  built  of  the  best  material,  neat  in 
appearance,  has  a  large  capacity,  economical  in  power  and 
steam,  and  is  a  money-maker  to  ice  cream  manufacturers,  con- 
denseries  and  creameries.  The  saving  on  water  and  power  to 
pump  would  soon  pay  for  this  entire  equipment. 

Apply  to 

THE  CREAM  PRODUCTION  CO. 

PORT  HURON,  MICHIGAN  Mfgs.  for  United  States 

B.  TRUDEL  &  CO. 

MONTREAL,  QUEBEC  Mfgs.  for  Canada 


CONDENSED  MILK  AND  MILK  POWDER 


393 


The  Dickerson  Vent  Hole  Filler  and  Sealer 

Baby  Machine      II      Tall  Machine      II  Combination    Machine 
for  6   oz.  cans          for  16   oz.  cans  for   16   and    12  oz. 


TALL  SIZE 
Dickersoii  Fillers  give  EFFICIENCY— ACCURACY— ECONOMY 

They  are  THE  WORLD'S  STANDARD 

The  cans  have  only  a  vent  hole.  They  are  filled  and  sealed 
continuously  and  automatically  on  the  same  machine.  ONE 
MACHINE  DOES  IT  ALL.  By  using  the  old  style  wide-open 
cans,  you  transfer  much  of  the  can  maker's  grief  to  your  filler 
room.  Get  COMPLETED  (vent  hole)  cans  and  a  Dickerson 
filler.  Besides  being  neater,  cleaner  and  safer,  vent  cans  cost 
less.  The  process  of  filling  and  sealing  is  also  much  cheaper. 
The  government  will  "get  you"  if  you  sell  short  weights. 
You'll  not  get  a  "thank  you"  for  a  surplus.  Fill  every  can  to 
correct  weight  (to  the  gram)  and  neither  shortage  nor  sur- 
plus will  worry  you. 

A  gram  A  can  A  year=! 
The  F.  G.  Dickerson  Co.,  549  W.Washington  Blvd.,  Chicago 


394 


CONDENSED  MILK  AND  MILK  POWDER 


Progress  Hoinogenizer 

Progress  Homogenizers  are  built  in  four  sizes.  Number  1 
handles  90  gallons  per  hour;  Number  2,  200  gallons;  Number  4, 
-HJO  gallons;  Number  8,  800  gallons.  Each  machine  is  built 
full  rated  capacity,  and  it  will  do  the  work  it  is  intended  for 
at  small  expense  and  to  excellent  advantage. 

This  machine  quickly  pays  its  cost,  and  oftimes  it  results 
in  a  saving  equal  to  many  times  its  cost  in  a  very  short  time. 
You  manufacturers  of  evaporated  milk  must  avoid-  the  waste 
which  may  be  occasioned  by  "separated"  milk.  The  Progress 
Homogenizer  so  breaks  up  the  fat  globules  that  the  cream 
cannot  possibly  separate.  It  will  not  injure  the  casein. 

Write  to  our  nearest  office  for  full  information  and  prices 
on  the  size  you  need.  Many  plants  have  several  of  these 
machines.  Tell  us  about  the  size  of  your  business  so  we  can 
judge  as  to  your  requirements.  "The  Davis-Watkins  Line" 
includes  everything  needed  in  the  manufacture  of  Dairy 
Products.  Let  us  quote  you  prices  and  co-operate  with  you. 

DAVIS  -ACTIONS  DAIRYMEN'S  MFG.CO. 


ADDRESS    Nl 

NORTH  CHICAGO.   ILL. 
JERSEY  CITY.  N.  J. 

KANSAS  CITY.   MO. 


DENVER.  COLO. 

SAN   FRANCISCO,  CAL. 


CONDENSED  MILK  AND  MILK  POWDER 


395 


Progress  Circular  Milk  Can  Washer 

Every  valve  is  accessible  and  easily  flushed.  Each  can  and 
cover  is  drained,  washed,  rinsed,  sterilized  and  dried  inside  and  out- 
side; all  in  a  few  minutes,  too,  and  with  a  reasonable  amount  of 
steam  and  power.  You  can't  beat  it  for  efficient,  economical  results. 

You  save  on  the  keeping  qualities  of  your  milk  by  reducing  the 
bacteria  count  to  the  minimum.  You  save  milk-can  money  because 
none  of  the  tin  is  scraped  off,  and  they  don't  rust  so  badly.  You 
save  labor  expense  in  your  plant.  The  Progress  can  washer  will  do 
all  these  things  for  you.  Figure  out  what  this  service  is  worth  to 
you. 

DAMS-\\&TKINS  DAIRYMEN'S  MFG.CO. 


ADDRESS    NEAREST    SALES    OFFICE 


NORTH  CHICAGO.  ILL. 
JERSEY  CITY.  N.  J. 

KANSAS  CITY.  MO. 


DENVER,  COLO. 

SAN   FRANCISCO.  CAL. 


396 


CONDENSED  MILK  AND  MILK  POWDER 


"Davis  Pasteurization" 

This  is  an  efficient  line  of  our  machinery  which  will 
properly  pasteurize  large  quantities  of  milk  at  low  operat- 
ing cost.  With  this  equipment  you  are  insured  a  natural 
raw  taste,  the  big  Davis  cream  line  and  a  low  bacteria 
count.  These  are  the  three  big  things  so  essential  to  the 
proper  building  of  any  milk  business. 

"Davis  Pasteurization"  machinery  is  automatic  in 
operation,  easily  cleaned,  requires  little  power  expense 
and  occupies  small  floor  space.  It  needs  practically  no 
attention  while  operating.  The  milk  is  all  inclosed  so 
there  is  no  loss  from  evaporation  and  no  chance  of  con- 
tamination. The  right  temperatures  are  applied  in  the 
right  way, 

This  equipment  will  solve  your  pasteurization  problem 
in  the  simplest  way,  insure  you  against  competition  and 
cut  your  cost  of  handling  to  a  minimum.  Write  our  near- 
est office  for  complete  information.  Tell  us  how  much 
milk  you  handle  daily.  Let  our  experts  help  you  with 
your  problems.  Such  action  on  your  part  obligates  you 
in  no  way,  and  it  may  help  you  more  than  you  think.  Do 
it  NOW. 

DAVIS  AV&TKINS  DAIRYMEN'S  MFG.GO, 


ADDRESS    NEAREST    SALES    OFFICE 


NORTH  CHICAGO,  ILL. 
JERSEY  CITY,  N.  J. 

KANSAS  CITY,  MO. 


DENVER.  COLO. 

SAN   FRANCISCO.  CAL. 


CONDENSED  MILK  AND  MILK  POWDER 


397 


A  Reliable  Butter  Maker 

Once  a  Disbrow  Owner,  always  a  Disbrow  Booster. 
Buttermakers  everywhere  proclaim  the  superiority  of  the 
Disbrow.  Built  strong  and  sturdy,  it  will  stand  up  well 
under  heavy  loads.  The"  quality  is  there.  It  is  like  a 
pure-bred  animal,  worthy  of  its  name  at  all  times. 

For  large  capacity  and  continuous  work  you  need  the 
Number  Eight  Heavy  Duty  or  the  Number  Eight  Giant. 
The  Giant  barrel  is  a  little  larger  in  diameter;  the  cast- 
ings and  chain  are  a  little  heavier.  Both  barrels  are  eight 
feet  long  on  the  inside. 

If  you  are  interested  in  knowing  the  detailed  information 
of  this  wonderfully  efficient,  combined  churn  and  worker, 
write  for  "The  Disbrow  Churn  Book."  It  is  free  and  there  is 
no  obligation.  There  are  smaller  sizes,  if  the  Number  Eight 
is  too  large.  The  free  book  shows  pictures  and  gives  com- 
plete information  on  the  Disbrow  Churn  your  business  needs. 
Send  for  it  NOW. 

DAVIS-ATKINS  DAIRYMEN'S  Mro.Ca 


ADDRESS  NEAREST  SALES  OFFICE 


NORTH  CHICAGO,   ILL. 
JERSEY  CITY.  N.  J. 

KANSAS  CITY.   MO. 


DENVER.  COLO. 

SAN   FRANCISCO.  CAL. 


398  CONDENSED  MILK  AND  MILK  POWDER 


DRY  BUTTERMILK 


OR 


BUTTERMILK  POWDER 

is  in  constantly  increasing  demand 
at  a  price  that  means 

BIG  PROFITS 

to  the  wide-awake  creameryman 
equipped   to  manufacture  same. 

Dry  Milk  Engineering  Co. 

is  building  and  installing  successful 

Buttermilk  Drying  Plants 

in  Dairy  sections  everywhere  that  are 
simple,  efficient  and  economical  to 
maintain  and  operate,  require  but 
little  space  and  power  and  insure 

MORE  REAL  PROFIT 

than  any  other  method  of 
Buttermilk    disposal. 

Full  details  and  suggestions  by  our  Dry  Milk  Experts  and 
Engineers  are  yours  for  the  asking. 


DRY  MILK  ENGINEERING  CO. 

139  N.  CLARK  ST.,  CHICAGO 


CONDENSED  MILK  AND  MILK  POWDER 


399 


UNIFORM  STERILIZATION! 


is  secured  by  using  the  Fort  Wayne  Sterilizer.  Built  in 
various  sizes,  from  a  small  Pilot  up  to  a  144-case  machine, 
it  will  handle  all  sizes. of  standard  cans  without  change  of 
equipment.  Let  us  tell  you  about  the  recent  improve- 
ments incorporated  in  this  sterilizer,  and  why  it  is  used 
by  all  the  leading  manufacturers  of  evaporated  milk. 

We  also  build  straight  line  and  rocker  arm  shakers  of  im- 
proved design,  steel  trays  and  tanks,  as  well  as  special 
machinery.  Our  new  plant  with  modern  equipment  en- 
ables us  to  give  good  service  at  a  reasonable  price. 

Tell  us  your  requirements  and  let  us  show  you  what  we 
can  do. 

THE  ENGINEERING  COMPANY 

1600  WINTER  STREET        FORT  WAYNE,  INDIANA 


400  CONDENSED  MILK  AND  MILK  POWDER 


Neither  Is  of  Recent  Origin 


The  condensed  milk  and  milk  powder  industry  is 
not  new,  yet  little  has  been  written  on  the  subject  to 
enlighten  the  manufacturer  on  its  many  complexities. 
Nevertheless,  it  has  always  been  the  opinion  of  those 
engaged  in  milk  and  milk  product  production  that  sani- 
tary cleanliness  must  prevail.  Due  to  the  persistent 
demand  for  cleanliness,  and  assisted  by  the  never  fail- 
ing service  rendered  by 


the  milk  and  milk  powder  industry  has  reached  a  very 
high  development. 

This  cleaner  not  only  appeals  to  the  producer  of 
milk  and  milk  products  because  it  establishes  the  most 
sanitary  and  cleanly  conditions,  but  also  because  it  does 
this  so  much  more  easily,  quickly,  economically  and 
profitably  than  other  cleaners. 

Your  supply-  house  will  fill  your 

order  on  our  money  back 

guarantee. 

It  Cleans  Clean. 

in  every  package. 


The  J.  B.  Ford  Co.,  Sole  Mfrs.,  Wyandotte,  Mich 


CONDENSED  MILK  AND  MILK  POWDER  401 


WHAT  DOES 


THREE  FUNDAMENTAL  PRINCIPLES 

The  different  uses  for  BK  are  based  on  three  funda- 
mental principles.  When  these  are  understood  it  gives 
an  appreciation  of  BK  and  a  knowledge  that  enables  man- 
ufacturers and  handlers  of  dairy  products  to  apply  it  in 
many  ways  to  lighten  labor  and  produce  purer  products. 

These  principles  are: 

1.  High  bacteriacidal  power 

2.  Solvent  Action 

3.  Harmlessness 

The  bacteria-destroying  power  of  BK  is  high,  so  that 
it  kills  the  bacteria  on  coming  in  contact  with  them. 

The  solvent  action  of  BK  on  albumins — milk  casein, 
etc.,  softens  the  accumulations  on  coils,  heaters,  pasteur- 
izers, pipes,  etc.,  making  the  cleaning  operation  easier. 
Where  the  metal  parts  of  equipment  are  not  already 
coated  with  casein  the  application  of  BK  before  the  daily 
run  prevents  a  milk  film  from  adhering  and  also  dissolves 
any  thin  albuminous  film  that  might  be  there.  This  sol- 
vent action  also  exposes  the  bacteria  to  prompt  destruc- 
tion. 

These  two  functions  of  BK  insure  a  high  degree  of 
sterilization  and  cleansing — also  great  economy  of  labor. 

BK  is  a  harmless  hypochlorite  such  as  used  by  the 
most  experienced  medical  men  in  and  on  the  human  body 
— adopted  by  the  great  surgeons  of  the  allied  armies 
after  trying  over  150  different  articles  for  protection  of 
health  and  foods  of  the  armies. 

The  amount  of  BK  needed  to  make  an  effective  steril- 
izing solution  is  very  small  and  the  amount  of  BK  left  on 
the  equipment  after  using  is  infinitesimal  and  negligible. 
Authoritative  Experiment  Station  bulletins  prove  this 
point  conclusively  in  their  tests  on  chemical  sterilizing. 

BK  is  easy  to  use  everywhere  for  purifying,  deodoriz- 
ing and  disinfecting.  BK  has  stood  the  test  of  time— it 
has  made  good.  Those  who  learn  its  helpfulness  become 
constant  users. 

GENERAL  LABORATORIES 

19  S.  DICKINSON  ST.  MADISON,  WIS. 


402 


CONDENSED  MILK  AND  MILK  POWDER 


GROEN 

Vertical  Condenser 
Copper  Vacuum  Pans 


Built  in 
3,  4,  5,  6  and  7  ft. 

Sizes. 


Large  Coil 
Inlets   and   Outlets 

for 
Exhaust  Steam. 


Write  for  Blueprint 

Specifications 

and  Prices. 


Deliveries  made  as 
promised. 


Manufacturers   of  Copper  Vacuum  Pans,   Hotwells, 

Steam  Jacketed  Kettles  and  Special 

Coppersmith  Work. 


GROEN  MFG.  CO.,  me 

Coppersmiths 
4529-37  Armitage  Ave.  Chicago,  U.  S.  A, 


CONDENSED  MILK  AND  MILK  POWDER 


403 


Jensen  Vertical  Coolers 


SPECIALLY  BUILT  FOR 
COOLING 


CONDENSED  AND  EVAPORATED  MILK 

ELIMINATE  CRYSTALLIZATION. 

Furnish  Correct  Amount  of  Agitation  to  Produce  a  Smooth 

Product.    Eliminate  Air  and  Gases  Thru  Rotation  of 

Double  Helical  Coil  During  Cooling  Process. 

PREVENT  CONTAMINATION 

as  all  Packing  and  Stuffing  Boxes  are  Outside  and  Above  the 

Machine. 

ASK  FOR  CATALOG  No.  20A. 

Jensen    Creamery    Machinery  Company 

Long  Island  City,  N.  Y.  Oakland,  California 

Southern  Distributor: 
BLANKE  MFG.  &  SUPPLY  CO.,  ST.  LOUIS,  MO. 


404 


CONDENSED  MILK  AND  MILK  POWDER 


HARRIS  COPPER  VACUUM  PAN 

FOR  MILK  CONDENSING 

AWARDED  GOLD  MEDAL 
PANAMA-PACIFIC  INTERNATIONAL  EXPOSITION 


ARTHUR  HARRIS  &  Co. 

Pioneer  Constructors  of 
MILK  CONDENSING  APPARATUS 


2.  1  2L-2.  1  S  CURTIS  STREET 


CHICAGO,   ILLINOIS 


CONDENSED  MILK  AND  MILK  POWDER  405 


Harris  Copper  Vacuum  Pans 


AND 


Milk  Condensing  Machinery 

Have  been  our  Specialty  for  over 
30  years.  Over  this  period  we  have 
continuously  produced  High 
Grade  Apparatus  which  has  given 
most  gratifying  results  both  in 
production  and  service.  Large 
capacity  Harris  Copper  Vacuum 
Pans  in  service  today  total  in  the 
hundreds. 

We  Solicit  Your  Inquiries  for 

VACUUM    PANS  STERILIZERS 

FOREWARMERS  SHAKERS 

VACUUM   PUMPS  LABELING    MACHINES 

COOLING  MACHINES  RUBBER   PACKED   COCKS 

PIPE    COOLERS  SAMPLERS 

RECEIVING    TANKS  SUPERHEATER    BULBS 

STORAGE  TANKS  COOLING   COILS 

FILLING    MACHINES  WEIGH   SCALE  TANKS 

PEEPHOLE  GLASSES,  ETC. 


Arthur  Harris  &  Go. 

Established    1884 

212-218  Curtis  St.  Chicago,  Illinois 


406 


CONDENSED  MILK  AND  MILK  POWDER 


The  Lathr  op -Paulson  Company 

Can  Washer  of  Super-Success.    No  Waste,  Less  Work, 
Bigger^andfBetter^Results. 


This  New  L-P  Entirely  Auto- 
matic Machine  has  Capacity 
up  to  TOO  Cans  and  Covers  per 
hour.  Practical  and  efficient 
in  every  way.  Embodies  all 
the  features  of  our  former 
machines  with  double  their 
efficiency,  at  less  cost. 


Aug.  20,  1907. 

Aug.  20,  1907. 

Sept.  14,  1909. 

Feb.  22,  1916. 

Dec.  4,  1917. 


,     864,131  Jan. 

.    864,133  Apr. 

.     934,404  Aug.     20,  1907 

.1,172,808  Mar. 


U.    S.    PATENTS 

8,  1918 1,252,453     Nov.     27,   1917... 

1,262,679    Dec.       4,  1917 


Apr. 


4,  1916. 
9,  1919. 


3,  1908 

.1,249,129    Feb.     15,  1910 

CANADIAN  PATENTS 

168,585    Nov.     11,  1919 

3,  1919 


864,132  Feb.  12,  1918... 
880,713  Dec.  31,  1918... 
949,121 


Nov.     11,  1919... 
192,647     Nov.     25,  1919... 


.1,247,692 
.1,249,130 
.1,255,896 
.!,£" 


193,885 


Other  U.    S.    and   Foreign   Patents    Pending 

NOTABLE  IMPROVED  FEATURES: 


Does  not  require  even   one  man 

to  operate. 
Machines    are    END    FED,    most 

convenient  for  disposal  of  can 

by  milk  dumper. 
Driven   by  motor  or    steam  tur-, 

bine  of  less  than  one  and  one-" 

half  horse  power. 
Less     than     one-quarter     horse 

power  consumed   in  automatic 

machine  drive. 

Water  consumption  cut  seventy- 
five  per  cent. 
Drying  capacity  DOUBLED.  Fan 

delivering    1800    cubic    feet    of 

dry,    sterile,    super-heated    air 

per  minute. 
WARM  SODA  SOLUTION  WASH 

— under  pressure  of  80  to   100 

pounds. 
CLEAR       SCALDING       WATER 

WASH  immediately    following 


under  pressure  of  80  to  100 
pounds. 

STEAM  STERILIZATION  under 
complete  control,  any  amount 
you  desire. 

Operating  at  the  rate  of  700  cans 
and  covers  per  hour.  EACH 
and  EVERY  CAN  receives 
THREE  to  FIVE  minutes  of 
hacteria-destroyingf  steriliza- 
tion. 

Insures  Clean,  Dry,  Sterile  re- 
ceptacles, for  the  conveyance 
of  product  from  producer  to 
manufacturer  at  lowest  pos- 
sible cost. 

Machines  have  the  unique  fea- 
ture of  handling  cans  as  fast 
or  as  slow  as  desired,  depend- 
ing solely  on  the  speed  they 
are  fed  to  machine,  and  cannot 
be  crowded  beyond  capacity. 


The  Lathrop-Paulson  Company  are  Milk  Can  Washing  Machine 
Specialists  and  Solicit  Your  Inquiries  and  Requirements 

THE  LATHROP-PAULSON  COMPANY 

2459  West  48th  Street,  Chicago,  Illinois 


CONDENSED  MILK  AND  MILK  POWDER  407 


Milk  and  Egg 
Drying  Machinery 


WE  have  over  one  hundred  plants 
in  successful  operation  using 
our  spray  process  in  United  States 
and  Foreign  Countries. 

We  supply  and  install  complete 
Milk  or  Egg  drying  plants  of  any  re- 
quired capacity,  guaranteeing  the 
highest  efficiency  at  the  lowest  cost, 
and  that  our  finished  products  are 
freely  soluble. 

We  build  a  tray  albumen  Egg 
Drier,  which  produces  a  crystal  or 
flake  product.  Also  a  Buttermilk 
Drier,  other  than  the  spray  process. 
Price  and  particulars  on  application. 

Write  for  Catalogue 


Milk  Drying  Machinery  Company 

Designers,  Manufacturers  and  Builders  of  Milk  and  Egg  Drying  Machin- 
ery. Patented  in  U.  S.  and  Foreign  Countries.         Established  in  1903. 

138  North  Clark  Street,  Chicago,  Illinois 

Suite  1017-18  City  Hall  Square  Building 


408 


CONDENSED  MILK  AND  MILK  POWDER 


Mojonnier  Milk  Tester  for  Butter  Fat  and  Total  Solids 

(Process  patented  April  3,  1917;  Apparatus  patented  February  5,   1918;  April  9,  1918;  June 

11,   1918,   and  August  5,   1919.) 

Other    patents    pending. 

Standard  Equipment 

in  all  up-to-date  ice  cream,  condensed  and  evaporated  milk 
plants  and  the  larger  fresh  milk  plants  includes  the 


Tester 


It  is  used  by  a  large  majority  of  the  manufacturers  of  evapo- 
rated milk/  and  with  it  they  standardize  their  product  to 
within  a  few  hundredths  of  1  per  cent  of  any  standard  de- 
sired upon  both  butter  fat  and  total  solids. 

OTHER  MOJONNIER  PRODUCTS: 
Mojonnier  Ice  Cream  Overrun  Tester. 
Mojonnier  Culture  Controller. 
Mojonnier  Evaporated  Milk  Controller. 
Mojonnier  Evaporated  Milk  Can  Polisher. 
Mojonnier  Evaporated  Milk  Can  Opener. 
Mojonnier  Composite  Sample  Bottles. 
Mojonnier  Steam  Pressure  Copper  Kettles. 

Extensive  line  of  scientific  apparatus  and  laboratory  supplies  for  chemical 
and  bacteriological  control  of  milk  products 

Further  information  cheer  ully  furnished  on  any  of  the  above  products. 


13/un.Co. 


MILK   ENGINEERS 

739  WEST  JACKSON  BLVD.,  CHICAGO 

Eastern  Office    ....     ......      200  Fifth  Avenue,  New  York,  N.  Y. 

Southern  Office      .......      4931  Margaretta  Avenue,  St.  Louis,  Mo. 

Western  Office  ......      2679  McAllister  Street,  San  Francisco,  Calif. 


CONDENSED  MILK  AND  MILK  POWDER 


409 


Are  You  Getting  the  Highest 
Efficiency  From  Your . 
Testing  Room  ? 


NAFIS 


SCIENTIFIC 
GLASSWARE 


WILL   HELP   YOU   TOWARDS 
THAT  GOAL  BECAUSE  OF  ITS 


Accuracy  and 
Quality. 


Nafis 


Testing 
Glassware 

is  the  result  of  years  of  experi- 
ence and  scientific  study.  It  is 
made  to  conform  with  the  specifi- 
cations of  the  United  States  Bu- 
reau of  Standards  as  well  as  those 
of  the  different  states. 
Test  Bottles  are  made  in  either 
the  regular  or  the  Circled  Gradua- 
tion style. 

Send  in  a  trial  order  and  judge 
for  yourself. 

If  your  dealer  cannot  supply  you 
with  Nafis  Glassware,  write  for 
our  illustrated  catalogue  and  list 
of  our  distributors. 

Louis  F.  Nafis,  Inc. 

Manufacturers  of  Scientific  Glassware  for 
Testing  Milk  and  Its  Products 

542-548    Washington   Boulevard 
CHICAGO,  U.  S.  A. 


410 


CONDENSED  MILK  AND  MILK  POWDER 


PFAUDLER 

GLASS  LINED  STEEL 
CONDENSED  MILK  EQUIPMENT 


TPhis  Tank  is  used  in  Condenseries  and 
-•-  Bottled  Milk  Plants  to  reduce  the  tem- 
perature of  incoming  milk.  It  is  jacketed 
for  brine  circulation,  may  be  equipped 
with  either  Air  or  Mechanical  Agitating 
Device,  and  the  Milk  Inlets  are  provided 
with  spreading  devices  which  spread  the 
milk  in  a  thin  film  over  the  brine-chilled 
tank  wall,  reducing  it  at  once  to  a  low 
temperature.  Sizes,  capacities  and  prices 
on  request. 


Pfautller    Glass  Lined    Steel 
Milk   Storage  Tank 


Pfaudler   Glass  Lined   Steel 
Jacketed    Forewarmer 


OF  A  U  D  L  E  R 

^  Fore  warm  - 
ers  are  made  in 
the  single-shell 
type  or  with  jacket  and  side  agitator, 
as  illustrated.  With  the  latter  the  major 
part  of  the  preheating  operation  may 
be  carried  out  without  the  introduction 
of  steam  and  finished  by  the  injection  of 
live  steam  with  the  regular  type  of 
steam  header.  It  may  be  had  with  or 
without  the  copper  cover  illustrated. 
Sizes,  capacities  and  prices  on  request. 


HPhis  Milk  Truck  Tank  is  divided 
*•  through  the  center  by  a  parti- 
tion head  which  is  open  at  the  top 
and  bottom  and  acts  as  a  baffle  to 
minimize  churning  of  the  contents. 
The  interior,  including  both  sides  of 
the  partition  head,  is  lined  with 
Pfaudler  Glass  Enamel,  which  ex- 
tends to  the  outer  edges  of  the  man- 
hole flanges  and  to  the  end  of  the 
outlets  located  at  the  underside  of 
the  tank. 

Write  for  Dairy  Equipment  Bulletin 

THE  PFAUDLER  COMPANY 

ROCHESTER,  N.  Y. 

NEW  YORK  CHICAGO  ST.  LOUIS  SAN  FRANCISCO 


Pfaudler    Glass  Lined    Steel    Milk 
Truck  Tank 


CONDENSED  MILK  AND  MILK.  POWDER  411 

How  To  Prevent  Streaks  and 
Mottles  in  Butter 

Prof.  Hunziker  asserts  that  streaks  and  mottles  in  butter 
are  caused  by: 

(1)  Incomplete  fusion  of  salt  and  water  in  butter. 

(2)  Faulty  Mechanical  condition  of  the  butter  workers. 

(3)  Overloading  of  the  machine. 

Not  one  of  these  causes  but  what  may  be  overcome  by  any 
buttermaker  who  takes  pride  in  his  product.  With  Colo- 
nial Salt  the  buttermaker  will  never  be  troubled  with  in- 
complete fusion.  The  other  two  causes  are  mechanical 
and  can  be  easily  remedied.  Flake  salt  dissolves  quicker 
than  cube  salt  of  the  same  size  grain.  Colonial  Salt  is  the 
only  all  flaked  Butter  Salt  on  the  market.  It  will  produce 
over-run,  color,  flavor  and  body.  Try  it  in  your  next 
batch  of  butter.  THE  SALT  THAT  MELTS  LIKE  SNOW 

FLAKES  AND   DISSOLVES   LIKE  MIST 

THE  COLONIAL  SALT  CO. 

AKRON,  OHIO 
CHICAGO^ BOSTON = ATLANTA  =  BUFFALO 


R  &  A  Hydraulic   Can  Washer,  Sterilizer  and 
Drier  for  Clean,  Dry  Sterile  Cans 


Fig.  610 
Two-tank  machine 

showing 
powerful  blower 
and  hot  air  drier 


RICE  &  ADAMS,  Inc. 


166-182  CHANDLER  STREET 
BUFFALO 


412  CONDENSED  MILK  AND  MILK  POWDER 

STERILIZERS 

In  All  Standard  Capacities 


1 


STERILIZER 
LOADING    END 


Equal  Heat  Distribution 

RAPID    LOADING 
AND  UNLOADING 


Our  Shakers  are  also  good 


C.  E.  ROGERS 

8731  Witt  Street  Detroit,  Michigan 


CONDENSED  MILK  AND  MILK  POWDER  413 

HIGH  TYPE  COPPER 

VACUUM 
PANS 


SAVE 

Fuel,  Water 
Milk,  Labor 


Largest 
Capacities 

Utilizing  either 
Live  or  Exhaust 
Steam 


Manufactured 
complete  by 


C.  E.  ROGERS 

8731  Witt  Street  Detroit,  Michigan 


4'14 


COND£NS£D    MlI,K    AND 


POWDER 


SARGENT'S  ELECTRIC  DRYING  OVEN 


(PATENTED) 


May  be  set  for  any  tempera- 
lure  from  70°  C.  to  150°  C. 
and  will  maintain  that  tem- 
perature indefinitely.  Al- 
most a  necessity  in  Milk 
Product  Laboratories  where 
the  maintenance  of  the  low- 
est usable  temperature  is 
)fJS)  imperative. 

Price  complete  with  six-foot 
cord,  plug-  and  thermometer. 
$35.00.  Wound  for  110-  or 
220-volt  current. 


Complete  catalogues  furnished 
upon    application. 


E.  H.  SARGENT  &  CO. 

Manufacturers,  Importers,  Dealers  in  Chemicals  and  Chemical 
Apparatus  of  High  Grade  only. 


155-165  East  Superior  Street 


C  H  I  C  A  GO 


Schaefer 
Manufacturing  Company 

BERLIN,  WISCONSIN 

Manufacturers  of 

Condensed  arid  Evaporated 

Milk  Machinery 


Sterilizers 

Shakers 

Test  Sterilizers 

Fillers 


Automatic 

Machinery 
Can  Conveyors 
Testers 


Can  Coolers  and 
Special  Machinery 

for  Special 

Purposes 


CONDENSED  MILK  AND  MILK  POWDER 


415 


Make  Your  Own  Cream 


rP.HE  Sharpies  Emulsifier  enables  you 
to  make  every  day,  the  exact  amount 
of  cream  needed.  No  shortage.  No 
surplus.  With  butter,  skim  milk  powder 
and  water  you  make  your  own  cream  in 
proper  quantities  at  the  proper  time 
with  this  machine. 


The 


Emulsifier 


—emulsifies  three  times  as  thoroughly 
as  any  other  emulsifier — 

— clarifies  the  product.  The  cost 
of  oil  and  repairs  is  guaranteed  not 
to  exceed  $2.00  a  year.  Sharpies 
is  the  most  economical. 

Write  to  nearest  office  for  catalog 
describing  the  Sharpies  Emulsi- 
fier and  containing  users'  letters. 


THE 

SHARPLES  SEPARATOR 
COMPANY 

West  Chester,  Pa. 


Chicago 


BRANCHES: 
San  Francisco 


Toronto 


416  CONDENSED  MILK  AND  MILK  POWDER 


Cemcoat 

White  Sanitary  Washable  Interior  Coating 

Cemcoat  is  a  snow-white  coating-  applied  like  paint. 
It  is  glossy  and  mirror-like  and  increases  the  light  by  re- 
flecting it  from  every  angle.  Paint  on  the  light  in  your 
Condensery — Cemcoat  your  walls.  The  Boston  Bio-chem- 
ical Laboratory  after  an  exhaustive  test  finds  that  Cem- 
coat affords  no  ground  for  accumulation  of  bacteria  and 
fungi.  Heat  and  cold  does  not  affect  Cemcoat  —  it  is 
water-proof. 

IAPIDOMTH 

••     TRADE-MARK       •• 

Dust-proofs  and  wear-proofs  concrete 
floors  by  chemical  action 

Lactic  acid  in  milk  causes  deterioration  of  concrete 
floors.  Prevent  these  conditions  by  flushing  on  Lapidolith, 
the  liquid  hardener. 

A  chemical  combination  is  effected  through  the  action 
of  Lapidolith  on  the  cement,  making  the  floor  granite-like 
and  non-absorbing. 

Many  dairies  and  condenseries  have  thoroughly  tested 
Lapidolith  for  a  number  of  years.  We  will  refer  you  to 
these  satisfied  users  and  send  samples  and  complete  in- 
formation. 

L.  Sonneborn  Sons,  Inc. 

264  Pearl  Street  NEW  YORK 

DEPT.  SO 


CONDENSED  MILK  AND  MILK  POWDER  417 

Are  you  going  to  make 

MILK  POWDER? 

//  you  are,  your  logical  choice  of 
drying  equipment  is   that  of  the 

SPRAY  DRYING  CORPORATION 

WHY? 

BECAUSE  all  the   milk   powder  is  recovered    within   the 

spray   chamber,    and   not   in   a  succession    of 

secondary  equipment. 
BECAUSE  no  milk  powder  escapes  with  the  outgoing  air, 

a  common  fault  with  spray  dryers. 
BECAUSE  it  eliminates  any  need  for  collecting  the  powder 

by  means  of  cyclone  dust  separators  and  great, 

rambling,  unsanitary  baffle  chambers. 
BECAUSE  of  the  low  fuel  power  and  labor  cost. 
BECAUSE  of  the  automatic  discharge  of  powder  directly 

into  the  barrels  without  conveying  machinery 

or  hand  shoveling. 
BECAUSE  the  space  occupied  is  only  a  fraction  of  that  of 

other  spray  systems. 
BECAUSE  no  high  pressure  pump  is  required  for  spraying 

the   milk,  steam  pressure  furnishing  the  force 

with  which  the  milk  is  sprayed. 
BECAUSE  we  install  these  dryers  at  your  .plant  complete 

in  every  detail,  and  set  in  operation  and  relieve 

you  of  any  concern  in  the  matter. 
BECAUSE  the  powder  is  freely  soluble  in  cold  water. 
BECAUSE  there  is  no  royalty  to  pay. 

We  build  these  dryers  to  operate  either  with 
fluid  milk  or  condensed  milk.     In  asking 
us  for  estimates  please  tell  us  how 
much  milk  you  wish  to  dry. 

Spray  Drying  Corporation 

50  VESEY  STREET  NEW  YORK  CITY 


418 


CONDENSED  MILK  AND  MILK  POWDER 


Yi^\  T  T  can  rec*uce  manufacturing  costs 
\^7    \^_J    and   improve  your  product  with 
TAG-ROESCH  Time-Temperature  Controllers— 

Because: 

Perfect  sterilization  of  every  batch 
of  milk  becomes  a  daily  and 
natural  occurrence  with  practi- 
cally no  labor  or  attention; 

Regardless  of  a  skilled  labor 
shortage,  the  quality  and  the 
quantity  of  production  are  safe- 
guarded forever,  because  an  in- 
experienced workman,  after  30 
minutes  of  instruction,  can  effi- 
ciently handle  a  number  of  steril- 
izers; 

A    rich    creamy    appearance    and 

uniformly  heavy  consistency  of 
the  finished  product  are  de- 
veloped— despite  the  fact  that  the 
condign,  properties,  and  con- 
centration of  the  milk  are  fixed — 
because  the  time  and  temperature 
cycles  are  adhered  to  rigidly; 

A  satisfactory  product  is  assured — seven  days  in  the  week 
and  52  weeks  in  the  year — in  exact  accordance  writh  the 
pre-determined  specifications,  because  the  vital  factors  of 
time  and  temperature  are  no  longer  a  "hit  or  miss"  propo- 
sition; 

No  separation  of  the  milk  when  subsequently  placed  in 
storage,  because  the  milk  always  obtains  sufficient  body 
or  viscosity; 

Hard,  unshakable  curds  are  avoided,  also  dark  color 
formation,  due  to  the  fact  that  excessive  time  and  tem- 
perature exposures  are  eliminated; 

Considerable  labor  and  steam  are  conserved,  which  sav- 
ings often  are  sufficient  to  more  than  pay  for  the  con- 
trollers in  one  year; 

TAG-ROESCH  Time-Temperature  Controllers  can  be  profit- 
ably employed  in  any  milk  condensery  because  this  device 
can  be  furnished  to  handle  automatically,  any  combination 
of  time  and  temperature — no  matter  how  unusual  or  com- 
plicated the  sterilizing  process  may  be. 


m 


LIABUE 


TEMPERATURE     ENGINEERS 
\Jd-88Thirty-ThJTd  St.  Brooklyn.N.Y. 


Write  for  Catalog  H-460 

and   include   details  of  your 

sterilizing  requirements. 


CONDENSED  MILK  AND  MILK  POWDER 


419 


TEMPERATURE  INSTRUMENTS, 

INDICATL1IRG-RECORDING-CONTROUL.ING 


NDICATlTCG-J 


cover  every  need  in  temperature  equipment  of 
condensed  milk  and  milk  powder  plants.  The 
executive  who  needs  temperature  instruments 
will  find  in  the  list  of  Tycos  products  just  what 
he  requires  for  each  especial  application. 


ANGLE  STEM 
THERMOMETER 


RECORDING 
THERMOMETER 


Instruments  for  every 
Temperature  Need 

Angle  and  Straight  Stem  Ther- 
mometers 

Engraved  Stem  Thermometers 

Paper  Scale  Dairy  Thermometers 

Dial  Thermometers 

Recording  and  IndexThermometers 

Temperature  and  Pressure  Regu- 
lators 

Recording  Pressure  and  Vacuum 
Gauges 

Hydrometers 

Bi-Record  Recording 
Thermometer 


Tycos  instruments  are  made  for  every 
purpose  in  the  Milk  Industry  from  the 
time  milk  enters  the  hot  well  until  it  is 
ready  to  be  removed  from  the  condenser 
or  vacuum  pan. 

It  will  be  a  privilege  for  us  to  send 
carefully  prepared  literature,  giv- 
ing valuable  information.  Simply 
ask  for  it.  No  obligation. 


SINGLE  DUTY 
THERMOMETER 


TAYLOR  INSTRUMENT   COMPANIES 

ROCHESTER,   N.  Y. 

There  is  a  Tycos  and  Taylor  Thermometer  for  Every  Purpose 


420 


CONDENSED  MILK  AND  MILK  POWDER 


Why  the  Leading 

Condensed  Milk  Makers 

Choose  Sturges  Cans 

— because  they  are  accurate — absolutely  true  to  measure. 
Sanitary — easy  to  clean  and  keep  clean.  Built  extra  strong 
to  withstand  long  service. 


are  built  of  the  highest  grade  of 
steel  plate,  carefully  tinned.  Saams 
soldered  smooth  as  a  china  bowl,  no 
places  for  milk  to  lodge  and  sour. 
Write  for  catalog  No.  111. 

STURGES  &  BURN  MFG.  CO. 

"Leaders  Since  1865" 
CHICACO,          -          ILLINOIS 


Torsion  Balance  Creamery  Scales 


The  Torsion 


Head  Office:  92  Reade  Street 

NEW  YORK,  N.  Y. 
Factory:  147-153  Eighth  Street 

JERSEY  CITY,  N.  J. 


No  Knife-Edges—No  Friction  — 

No  Wear 
SENSITIVE  and  ACCURATE 

Tares   and   balances   in  one  operation. 

No  loose  parts  to  shift.  Work- 
ing parts  practically  in  one 
piece. 

Torsion  Balance  bottle  Cream 
Test  Scale,  Style  1500,  used 
by  collection  stations,  cream- 
eries, etc.,  on  account  of  its 
extreme  accuracy. 

Your  profits  depend  on  your 
tests  as  much  as  anything 
else,  probably  more  so. 

Christian  Becker 
Analytical   Balances 

Balance  Co. 

31  West  Lake  Street 

Branches:  <^  CHICAGO,  ILL. 

49  California  Street 
SAN  FRANCISCO,  CAL. 


CONDENSED  MILK  AND  MILK  POWDER 


421 


CONDENSERY  and 
Powder  Plant  Pumps 


Wet  Vacuum 
Pumps  for  ex- 
hausting Milk 
Pans  manufac- 
tured in  all  re- 
quired sizes  and 
styles. 


SPECIAL 

HIGH 

PRESSURE 

PUMPS 

FOR 

Cooling 

Sweetened  Con- 
densed Milk 

OR 

Spraying   into 
Drying  Cabinets 

Bulletins  and  Detail  Information  Always  Available 

UNION  STEAM  PUMP  CO 

BATTLE,  CREEK,  MICH. 


422  CONDENSED  MILK  AND  MILK  POWDER 

COMPLETE 

Pumping  Equipment 


FOR 


Condensed  Milk  and  Milk  Powder  Plants 

STEAM,  BELT  OR  MOTOR  DRIVEN  FOR 
ANY  SERVICE,  CAPACITY  OR  PRESSURE 

WELL  PUMPS 

TANK  PUMPS  Spray  Pumps 

BOILER  PUMPS 
BRINE  PUMPS 

VACUUM  PUMPS 
FILTER  PUMPS 

Viscolizers  MILK  PUMPS 

COOLING  PUMPS 

All  listed  and  described  in  Bulletin  No.  57 


THE  FACTORY  BEHIND  THE  GOODS 


UNION   STEAM  PUMP  GO 

BATTLE  CREEK,  MICH. 


CONDENSED  MILK  AND  MILK  POWDER 


423 


The  Highest   Development  in  the   Art  of 
Treating  Evaporated  Milk  to  Pre- 
vent the  Separation  of  Butter 
Fat  without  disturbing  the 
Natural    Emulsion  of 
Casein  and  Albumin 


VISCOLIZER— SOO-GALL.ON  CAPACITY 


Specially  Constructed  for  Condenseries 
Designed  as  High  Pressure  Pumps  Should  be 

BUILT— PATENTED— GUARANTEED  BY 

Union  Steam  Pump  Co.,  Battle  Creek,  Mich. 


SALES  AND  SERVICE  BY 

John  W.  Ladd  Co.,  Detroit — Cleveland 

Cherry-Bassett  Co.,  Baltimore — Philadelphia 


424 


CONDENSED  MILK  AND  MILK  POWDER 


THE  BUTTER 
INDUSTRY 

BY    O.     F.     HUNZIKER 


712  pages  and  over 
100  illustrations. 

The  information 
contained  in  this 
book  is  new  and  not 
generally  known 
even  among  the 
most  progressive 
creameries  and  milk 
products  factories. 


PUBLISHED  BY  THE  AUTHOR. 


PRICE  $5.75 


•A  3  U7 

r       HlanfMKf 


JAN  10  1933 


YC  20714 


. 


492HJ9 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

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